As a technique that coexists with unicast and broadcast, the multicast technique effectively addresses the issue of point-to-multipoint data transmission. By enabling high-efficiency point-to-multipoint data transmission over a network, multicast greatly saves network bandwidth and reduces network load.

By using multicast technology, a network operator can easily provide bandwidth-critical and time-critical information services. These services include live webcasting, Web TV, distance learning, telemedicine, Web radio, and real-time video conferencing.

Information transmission techniques

The information transmission techniques include unicast, broadcast, and multicast.

Unicast

In unicast transmission, the information source must send a separate copy of information to each host that needs the information.

Figure 1 Unicast transmission

In Figure 1, Host B, Host D, and Host E need the information. A separate transmission channel must be established from the information source to each of these hosts.

In unicast transmission, the traffic transmitted over the network is proportional to the number of hosts that need the information. If a large number of hosts need the information, the information source must send a separate copy of the same information to each of these hosts. Sending many copies can place a tremendous pressure on the information source and the network bandwidth.

Unicast is not suitable for batch transmission of information.

Broadcast

In broadcast transmission, the information source sends information to all hosts on the subnet, even if some hosts do not need the information.

Figure 2 Broadcast transmission

In Figure 2, only Host B, Host D, and Host E need the information. If the information is broadcast to the subnet, Host A and Host C also receive it. In addition to information security issues, broadcasting to hosts that do not need the information also causes traffic flooding on the same subnet.

Broadcast is disadvantageous in transmitting data to specific hosts. Moreover, broadcast transmission is a significant waste of network resources.

Multicast

Multicast provides point-to-multipoint data transmissions with the minimum network consumption. When some hosts on the network need multicast information, the information sender, or multicast source, sends only one copy of the information. Multicast distribution trees are built through multicast routing protocols, and the packets are replicated only on nodes where the trees branch.

Figure 3 Multicast transmission

The multicast source sends only one copy of the information to a multicast group. Host B, Host D, and Host E, which are information receivers, must join the multicast group. The routers on the network duplicate and forward the information based on the distribution of the group members. Finally, the information is correctly delivered to Host B, Host D, and Host E.

To summarize, multicast has the following advantages:

· Advantages over unicast—Multicast data is replicated and distributed until it flows to the farthest-possible node from the source. The increase of receiver hosts will not remarkably increase the load of the source or the usage of network resources.

· Advantages over broadcast—Multicast data is sent only to the receivers that need it. This saves network bandwidth and enhances network security. In addition, multicast data is not confined to the same subnet.

Multicast features

· A multicast group is a multicast receiver set identified by an IP multicast address. Hosts must join a multicast group to become members of the multicast group before they receive the multicast data addressed to that multicast group. Typically, a multicast source does not need to join a multicast group.

· A multicast source is an information sender. It can send data to multiple multicast groups at the same time. Multiple multicast sources can send data to the same multicast group at the same time.

· The group memberships are dynamic. Hosts can join or leave multicast groups at any time. Multicast groups are not subject to geographic restrictions.

· Multicast routers or Layer 3 multicast devices are routers or Layer 3 switches that support Layer 3 multicast. They provide multicast routing and manage multicast group memberships on stub subnets with attached group members. A multicast router itself can be a multicast group member.

For a better understanding of the multicast concept, you can compare multicast transmission to the transmission of TV programs.

Table 1 Comparing TV program transmission and multicast transmission

TV program transmission	Multicast transmission
A TV station transmits a TV program through a channel.	A multicast source sends multicast data to a multicast group.
A user tunes the TV set to the channel.	A receiver joins the multicast group.
The user starts to watch the TV program transmitted by the TV station on the channel.	The receiver starts to receive the multicast data sent by the source to the multicast group.
The user turns off the TV set or tunes to another channel.	The receiver leaves the multicast group or joins another group.

Common notations in multicast

The following notations are commonly used in multicast transmission:

· (*, G)—Rendezvous point tree (RPT), or a multicast packet that any multicast source sends to multicast group G. The asterisk (*) represents any multicast source, and "G" represents a specific multicast group.

· (S, G)—Shortest path tree (SPT), or a multicast packet that multicast source "S" sends to multicast group "G." "S" represents a specific multicast source, and "G" represents a specific multicast group.

Multicast benefits and applications

Multicast benefits

· Enhanced efficiency—Reduces the processor load of information source servers and network devices.

· Optimal performance—Reduces redundant traffic.

· Distributed application—Enables point-to-multipoint applications at the price of minimum network resources.

Multicast applications

· Multimedia and streaming applications, such as Web TV, Web radio, and real-time video/audio conferencing

· Communication for training and cooperative operations, such as distance learning and telemedicine

· Data warehouse and financial applications (stock quotes)

· Any other point-to-multipoint application for data distribution

Multicast models

Based on how the receivers treat the multicast sources, the multicast models include any-source multicast (ASM), source-filtered multicast (SFM), and source-specific multicast (SSM).

ASM model

In the ASM model, any multicast sources can send information to a multicast group. Receivers can join a multicast group and get multicast information addressed to that multicast group from any multicast sources. In this model, receivers do not know the positions of the multicast sources in advance.

SFM model

The SFM model is derived from the ASM model. To a multicast source, the two models appear to have the same multicast membership architecture.

The SFM model functionally extends the ASM model. The upper-layer software checks the source address of received multicast packets and permits or denies multicast traffic from specific sources. The receivers obtain the multicast data from only part of the multicast sources. To a receiver, multicast sources are not all valid, but are filtered.

SSM model

The SSM model provides a transmission service that enables multicast receivers to specify the multicast sources in which they are interested.

In the SSM model, receivers have already determined the locations of the multicast sources. This is the main difference between the SSM model and the ASM model. In addition, the SSM model uses a different multicast address range than the ASM/SFM model. Dedicated multicast forwarding paths are established between receivers and the specified multicast sources.

Multicast architecture

IP multicast addresses the following issues:

· Where should the multicast source transmit information to? (Multicast addressing.)

· What receivers exist on the network? (Host registration.)

· Where is the multicast source that will provide data to the receivers? (Multicast source discovery.)

· How is the information transmitted to the receivers? (Multicast routing.)

IP multicast is an end-to-end service. The multicast architecture involves the following parts:

· Addressing mechanism—A multicast source sends information to a group of receivers through a multicast address.

· Host registration—Receiver hosts can join and leave multicast groups dynamically. This mechanism is the basis for management of group memberships.

· Multicast routing—A multicast distribution tree (a forwarding path tree for multicast data on the network) is constructed for delivering multicast data from a multicast source to receivers.

· Multicast applications—A software system that supports multicast applications, such as video conferencing, must be installed on multicast sources and receiver hosts. The TCP/IP stack must support reception and transmission of multicast data.

Multicast addresses

IP multicast addresses

· IPv4 multicast addresses:

IANA assigned the Class D address block (224.0.0.0 to 239.255.255.255) to IPv4 multicast.

Table 2 Class D IP address blocks and description

Address block	Description
224.0.0.0 to 224.0.0.255	Reserved permanent group addresses. The IP address 224.0.0.0 is reserved. Other IP addresses can be used by routing protocols and for topology searching, protocol maintenance, and so on. Table 3 lists common permanent group addresses. A packet destined for an address in this block will not be forwarded beyond the local subnet regardless of the TTL value in the IP header.
224.0.1.0 to 238.255.255.255	Globally scoped group addresses. This block includes the following types of designated group addresses: · 232.0.0.0/8—SSM group addresses. · 233.0.0.0/8—Glop group addresses.
239.0.0.0 to 239.255.255.255	Administratively scoped multicast addresses. These addresses are considered locally unique rather than globally unique. You can reuse them in domains administered by different organizations without causing conflicts. For more information, see RFC 2365.

NOTE:

Glop is a mechanism for assigning multicast addresses between different ASs. By filling an AS number into the middle two bytes of 233.0.0.0, you get 255 multicast addresses for that AS. For more information, see RFC 2770.

Table 3 Common permanent multicast group addresses

Address	Description
224.0.0.1	All systems on this subnet, including hosts and routers.
224.0.0.2	All multicast routers on this subnet.
224.0.0.3	Unassigned.
224.0.0.4	DVMRP routers.
224.0.0.5	OSPF routers.
224.0.0.6	OSPF designated routers and backup designated routers.
224.0.0.7	Shared Tree (ST) routers.
224.0.0.8	ST hosts.
224.0.0.9	RIPv2 routers.
224.0.0.11	Mobile agents.
224.0.0.12	DHCP server/relay agent.
224.0.0.13	All Protocol Independent Multicast (PIM) routers.
224.0.0.14	RSVP encapsulation.
224.0.0.15	All Core-Based Tree (CBT) routers.
224.0.0.16	Designated SBM.
224.0.0.17	All SBMs.
224.0.0.18	VRRP.

· IPv6 multicast addresses:

Figure 4 IPv6 multicast format

The following describes the fields of an IPv6 multicast address:

? 0xFF—The most significant eight bits are 11111111.

? Flags—The Flags field contains four bits.

Figure 5 Flags field format

Table 4 Flags field description

Bit	Description
0	Reserved, set to 0.
R	· When set to 0, this address is an IPv6 multicast address without an embedded RP address. · When set to 1, this address is an IPv6 multicast address with an embedded RP address. (The P and T bits must also be set to 1.)
P	· When set to 0, this address is an IPv6 multicast address not based on a unicast prefix. · When set to 1, this address is an IPv6 multicast address based on a unicast prefix. (The T bit must also be set to 1.)
T	· When set to 0, this address is an IPv6 multicast address permanently-assigned by IANA. · When set to 1, this address is a transient, or dynamically assigned IPv6 multicast address.

? Scope—The Scope field contains four bits, which represent the scope of the IPv6 internetwork for which the multicast traffic is intended.

Table 5 Values of the Scope field

Value	Meaning
0, F	Reserved.
1	Interface-local scope.
2	Link-local scope.
3	Subnet-local scope.
4	Admin-local scope.
5	Site-local scope.
6, 7, 9 through D	Unassigned.
8	Organization-local scope.
E	Global scope.

? Group ID—The Group ID field contains 112 bits. It uniquely identifies an IPv6 multicast group in the scope that the Scope field defines.

Ethernet multicast MAC addresses

· IPv4 multicast MAC addresses:

As defined by IANA, the most significant 24 bits of an IPv4 multicast MAC address are 0x01005E. Bit 25 is 0, and the other 23 bits are the least significant 23 bits of an IPv4 multicast address.

Figure 6 IPv4-to-MAC address mapping

The most significant four bits of an IPv4 multicast address are fixed at 1110. In an IPv4-to-MAC address mapping, five bits of the IPv4 multicast address are lost. As a result, 32 IPv4 multicast addresses are mapped to the same IPv4 multicast MAC address. A device might receive unwanted multicast data at Layer 2 processing, which needs to be filtered by the upper layer.

· IPv6 multicast MAC addresses:

As defined by IANA, the most significant 16 bits of an IPv6 multicast MAC address are 0x3333. The least significant 32 bits are mapped from the least significant 32 bits of an IPv6 multicast address. Therefore, the problem of duplicate IPv6-to-MAC address mapping also arises like IPv4-to-MAC address mapping.

Figure 7 IPv6-to-MAC address mapping

Multicast protocols

IMPORTANT:

The device does not support Layer 3 multicast protocols and the following Layer 2 multicast protocols:

· Multicast VLAN/IPv6 multicast VLAN.

· PIM snooping/IPv6 PIM snooping.

Multicast protocols include the following categories:

· Layer 3 and Layer 2 multicast protocols:

? Layer 3 multicast refers to IP multicast operating at the network layer.

Layer 3 multicast protocols—IGMP, MLD, PIM, IPv6 PIM, MSDP, MBGP, and IPv6 MBGP.

? Layer 2 multicast refers to IP multicast operating at the data link layer.

Layer 2 multicast protocols—IGMP snooping, MLD snooping, PIM snooping, IPv6 PIM snooping, multicast VLAN, and IPv6 multicast VLAN.

· IPv4 and IPv6 multicast protocols:

? For IPv4 networks—IGMP snooping, PIM snooping, multicast VLAN, IGMP, PIM, MSDP, and MBGP.

? For IPv6 networks—MLD snooping, IPv6 PIM snooping, IPv6 multicast VLAN, MLD, IPv6 PIM, and IPv6 MBGP.

This section provides only general descriptions about applications and functions of the Layer 2 and Layer 3 multicast protocols in a network. For more information about these protocols, see the related chapters.

Layer 3 multicast protocols

Layer 3 multicast protocols include multicast group management protocols and multicast routing protocols.

Figure 8 Positions of Layer 3 multicast protocols

· Multicast group management protocols:

Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) protocol are multicast group management protocols. Typically, they run between hosts and Layer 3 multicast devices that directly connect to the hosts to establish and maintain multicast group memberships.

· Multicast routing protocols:

A multicast routing protocol runs on Layer 3 multicast devices to establish and maintain multicast routes and correctly and efficiently forward multicast packets. Multicast routes constitute loop-free data transmission paths (also known as multicast distribution trees) from a data source to multiple receivers.

Layer 2 multicast protocols

Layer 2 multicast protocols include IGMP snooping, MLD snooping, PIM snooping, IPv6 PIM snooping, multicast VLAN, and IPv6 multicast VLAN.

Figure 9 Positions of Layer 2 multicast protocols

· IGMP snooping and MLD snooping:

IGMP snooping and MLD snooping are multicast constraining mechanisms that run on Layer 2 devices. They manage and control multicast groups by monitoring and analyzing IGMP or MLD messages exchanged between the hosts and Layer 3 multicast devices. This effectively controls the flooding of multicast data in Layer 2 networks.

· PIM snooping and IPv6 PIM snooping:

PIM snooping and IPv6 PIM snooping run on Layer 2 devices. They work with IGMP snooping or MLD snooping to analyze received PIM messages. Then, they add the ports that are interested in specific multicast data to a PIM snooping routing entry or IPv6 PIM snooping routing entry. In this way, multicast data can be forwarded to only the ports that are interested in the data.

· Multicast VLAN and IPv6 multicast VLAN:

Multicast VLAN or IPv6 multicast VLAN runs on a Layer 2 device in a multicast network where multicast receivers for the same group exist in different VLANs. With these protocols, the Layer 3 multicast device sends only one copy of multicast to the multicast VLAN or IPv6 multicast VLAN on the Layer 2 device. This method avoids waste of network bandwidth and extra burden on the Layer 3 device.

Configuring IGMP snooping

Overview

IGMP snooping runs on a Layer 2 device as a multicast constraining mechanism to improve multicast forwarding efficiency. It creates Layer 2 multicast forwarding entries from IGMP packets that are exchanged between the hosts and the router.

As shown in Figure 10, when IGMP snooping is not enabled, the AC floods multicast packets to all hosts in a VLAN. When IGMP snooping is enabled, the AC forwards multicast packets of known multicast groups only to the receivers.

Figure 10 Multicast packet transmission without and with IGMP snooping

IGMP snooping ports

As shown in Figure 11, IGMP snooping runs on Device A and Device B, and Host A and Host C are receivers in a multicast group. IGMP snooping ports are divided into member ports and router ports.

Figure 11 IGMP snooping ports

Router ports

On an IGMP snooping Layer 2 device, the ports toward Layer 3 multicast devices are called router ports. In Figure 11, GigabitEthernet 1/0/1 of Device A and GigabitEthernet 1/0/1 of Device B are router ports.

Router ports contain the following types:

· Dynamic router port—When a port receives an IGMP general query whose source address is not 0.0.0.0, the port is added into the dynamic router port list. At the same time, an aging timer is started for the port. If the port receives an IGMP general query before the timer expires, the timer is reset. If the port does not receive an IGMP general query when the timer expires, the port is removed from the dynamic router port list.

· Static router port—When a port is statically configured as a router port, it is added into the static router port list. The static router port does not age out, and it can be deleted only manually.

Do not confuse the "router port" in IGMP snooping with the "routed interface" commonly known as the "Layer 3 interface." The router port in IGMP snooping is a Layer 2 interface.

Member ports

On an IGMP snooping Layer 2 device, the ports toward receiver hosts are called member ports. In Figure 11, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 of Device A and GigabitEthernet 1/0/2 of Device B are member ports.

Member ports contain the following types:

· Dynamic member port—When a port receives an IGMP report, it is added to the associated dynamic IGMP snooping forwarding entry as an outgoing interface. At the same time, an aging timer is started for the port. If the port receives an IGMP report before the timer expires, the timer is reset. If the port does not receive an IGMP report when the timer expires, the port is removed from the associated dynamic forwarding entry.

· Static member port—When a port is statically configured as a member port, it is added to the associated static IGMP snooping forwarding entry as an outgoing interface. The static member port does not age out, and it can be deleted only manually.

Unless otherwise specified, router ports and member ports in this document include both static and dynamic router ports and member ports.

How IGMP snooping works

The ports in this section are dynamic ports. For information about how to configure and remove static ports, see "Configuring static ports."

IGMP messages types include general query, IGMP report, and leave message. An IGMP snooping-enabled Layer 2 device performs differently depending on the message types.

General query

The IGMP querier periodically sends IGMP general queries to all hosts and routers on the local subnet to check for the existence of multicast group members.

After receiving an IGMP general query, the Layer 2 device forwards the query to all ports in the VLAN except the receiving port. The Layer 2 device also performs one of the following actions:

· If the receiving port is a dynamic router port in the dynamic router port list, the Layer 2 device restarts the aging timer for the port.

· If the receiving port does not exist in the dynamic router port list, the Layer 2 device adds the port to the dynamic router port list. It also starts an aging timer for the port.

IGMP report

A host sends an IGMP report to the IGMP querier for the following purposes:

· Responds to queries if the host is a multicast group member.

· Applies for a multicast group membership.

After receiving an IGMP report from a host, the Layer 2 device forwards the report through all the router ports in the VLAN. It also resolves the address of the reported multicast group, and looks up the forwarding table for a matching entry as follows:

· If no match is found, the Layer 2 device creates a forwarding entry with the receiving port as an outgoing interface. It also marks the receiving port as a dynamic member port and starts an aging timer for the port.

· If a match is found but the matching forwarding entry does not contain the receiving port, the Layer 2 device adds the receiving port to the outgoing interface list. It also marks the receiving port as a dynamic member port and starts an aging timer for the port.

· If a match is found and the matching forwarding entry contains the receiving port, the Layer 2 device restarts the aging timer for the port.

In an application with a group policy configured on an IGMP snooping-enabled Layer 2 device, when a user requests a multicast program, the user's host initiates an IGMP report. After receiving this report, the Layer 2 device resolves the multicast group address in the report and performs ACL filtering on the report. If the report passes ACL filtering, the Layer 2 device creates an IGMP snooping forwarding entry for the multicast group with the receiving port as an outgoing interface. Otherwise, the Layer 2 device drops this report, in which case the multicast data for the multicast group is not sent to this port, and the user cannot retrieve the program.

A Layer 2 device does not forward an IGMP report through a non-router port because of the host IGMP report suppression mechanism.

Leave message

An IGMPv1 receiver host does not send any leave messages when it leaves a multicast group. The Layer 2 device cannot immediately update the status of the port that connects to the receiver host. The Layer 2 device does not remove the port from the outgoing interface list in the associated forwarding entry until the aging time for the group expires.

An IGMPv2 or IGMPv3 host sends an IGMP leave message when it leaves a multicast group.

When the Layer 2 device receives an IGMP leave message on a dynamic member port, the Layer 2 device first examines whether a forwarding entry matches the group address in the message.

· If no match is found, the Layer 2 device discards the IGMP leave message.

· If a match is found but the receiving port is not an outgoing interface in the forwarding entry, the Layer 2 device discards the IGMP leave message.

· If a match is found and the receiving port is not the only outgoing interface in the forwarding entry, the Layer 2 device performs the following actions:

? Discards the IGMP leave message.

? Sends an IGMP group-specific query to identify whether the group has active receivers attached to the receiving port.

? Sets the aging timer for the receiving port to twice the IGMP last member query interval.

· If a match is found and the receiving port is the only outgoing interface in the forwarding entry, the Layer 2 device performs the following actions:

? Forwards the IGMP leave message to all router ports in the VLAN.

? Sends an IGMP group-specific query to identify whether the group has active receivers attached to the receiving port.

? Sets the aging timer for the receiving port to twice the IGMP last member query interval.

After receiving the IGMP leave message on a port, the IGMP querier resolves the multicast group address in the message. Then, it sends an IGMP group-specific query to the multicast group through the receiving port.

After receiving the IGMP group-specific query, the Layer 2 device forwards the query through all its router ports in the VLAN and all member ports of the multicast group. Then, it waits for the responding IGMP report from the directly connected hosts. For the dynamic member port that received the leave message, the Layer 2 device also performs one of the following actions:

· If the port receives an IGMP report before the aging timer expires, the Layer 2 device resets the aging timer.

· If the port does not receive an IGMP report when the aging timer expires, the Layer 2 device removes the port from the forwarding entry for the multicast group.

Protocols and standards

RFC 4541, Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches

Command and hardware compatibility

The WX1800H series access controllers do not support the slot keyword or the slot-number argument.

IGMP snooping configuration task list

Tasks at a glance
Configuring basic IGMP snooping features: · (Required.) Enabling IGMP snooping · (Optional.) Specifying an IGMP snooping version · (Optional.) Setting the maximum number of IGMP snooping forwarding entries · (Optional.) Setting the IGMP last member query interval
(Optional.) Configuring IGMP snooping port features: · Setting aging timers for dynamic ports · Configuring static ports · Configuring a port as a simulated member host · Enabling fast-leave processing · Disabling a port from becoming a dynamic router port
(Optional.) Configuring the IGMP snooping querier: · Enabling the IGMP snooping querier · Configuring parameters for IGMP general queries and responses
(Optional.) Configuring parameters for IGMP messages: · Configuring source IP addresses for IGMP messages · Setting the 802.1p priority for IGMP messages
(Optional.) Configuring IGMP snooping policies: · Configuring a multicast group policy · Enabling dropping unknown multicast data · Enabling IGMP report suppression · Setting the maximum number of multicast groups on a port · Enabling the multicast group replacement feature

Tasks at a glance

Configuring basic IGMP snooping features:

· (Required.) Enabling IGMP snooping

· (Optional.) Specifying an IGMP snooping version

· (Optional.) Setting the maximum number of IGMP snooping forwarding entries

· (Optional.) Setting the IGMP last member query interval

(Optional.) Configuring IGMP snooping port features:

· Setting aging timers for dynamic ports

· Configuring static ports

· Configuring a port as a simulated member host

· Enabling fast-leave processing

· Disabling a port from becoming a dynamic router port

(Optional.) Configuring the IGMP snooping querier:

· Enabling the IGMP snooping querier

· Configuring parameters for IGMP general queries and responses

(Optional.) Configuring parameters for IGMP messages:

· Configuring source IP addresses for IGMP messages

· Setting the 802.1p priority for IGMP messages

(Optional.) Configuring IGMP snooping policies:

· Configuring a multicast group policy

· Enabling dropping unknown multicast data

· Enabling IGMP report suppression

· Setting the maximum number of multicast groups on a port

· Enabling the multicast group replacement feature

The IGMP snooping configurations made on Layer 2 aggregate interfaces do not interfere with the configurations made on member ports. In addition, the configurations made on Layer 2 aggregate interfaces do not take part in aggregation calculations. The configuration made on a member port of the aggregate group takes effect after the port leaves the aggregate group.

Configuring basic IGMP snooping features

Before you configure basic IGMP snooping features, complete the following tasks:

· Configure VLANs.

· Determine the IGMP snooping version.

· Determine the maximum number of IGMP snooping forwarding entries.

· Determine the IGMP last member query interval.

Enabling IGMP snooping

When you enable IGMP snooping, follow these restrictions and guidelines:

· You must enable IGMP snooping globally before you enable it for a VLAN.

· IGMP snooping configuration made in VLAN view takes effect only on the member ports in that VLAN.

· You can enable IGMP snooping for the specified VLANs in IGMP-snooping view or for a VLAN in VLAN view. For a VLAN, the configuration in VLAN view has the same priority as the configuration in IGMP-snooping view, and the most recent configuration takes effect.

To enable IGMP snooping for the specified VLANs:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable IGMP snooping globally and enter IGMP-snooping view.	igmp-snooping	By default, IGMP snooping is globally disabled.
3. Enable IGMP snooping for the specified VLANs.	enable vlan vlan-list	By default, IGMP snooping is disabled for a VLAN.

To enable IGMP snooping for a VLAN:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable IGMP snooping globally and enter IGMP-snooping view.	igmp-snooping	By default, IGMP snooping is globally disabled.
3. Return to system view.	quit	N/A
4. Enter VLAN view.	vlan vlan-id	N/A
5. Enable IGMP snooping for the VLAN.	igmp-snooping enable	By default, IGMP snooping is disabled in a VLAN.

Specifying an IGMP snooping version

Different IGMP snooping versions process different versions of IGMP messages.

· IGMPv2 snooping processes IGMPv1 and IGMPv2 messages, but it floods IGMPv3 messages in the VLAN instead of processing them.

· IGMPv3 snooping processes IGMPv1, IGMPv2, and IGMPv3 messages.

If you change IGMPv3 snooping to IGMPv2 snooping, the device does the following:

· Clears all IGMP snooping forwarding entries that are dynamically added.

· Keeps static IGMPv3 snooping forwarding entries (*, G).

· Clears static IGMPv3 snooping forwarding entries (S, G), which will be restored when IGMP snooping is switched back to IGMPv3 snooping.

For more information about static IGMP snooping forwarding entries, see "Configuring static ports."

You can specify the version for the specified VLANs in IGMP-snooping view or for a VLAN in VLAN view. For a VLAN, the configuration in VLAN view has the same priority as the configuration in IGMP-snooping view, and the most recent configuration takes effect.

To specify an IGMP snooping version for the specified VLANs:

Step	Command	Remarks
6. Enter system view.	system-view	N/A
7. Enable IGMP snooping globally and enter IGMP-snooping view.	igmp-snooping	N/A
8. Specify an IGMP snooping version for the specified VLANs.	version version-number vlan vlan-list	The default setting is 2.

To specify an IGMP snooping version for a VLAN:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Specify an IGMP snooping version for the VLAN.	igmp-snooping version version-number	The default setting is 2.

Setting the maximum number of IGMP snooping forwarding entries

You can modify the maximum number of IGMP snooping forwarding entries, including dynamic entries and static entries. When the number of forwarding entries on the device reaches the upper limit, the device does not automatically remove any existing entries. To allow new entries to be created, H3C recommends that you manually remove some entries.

To set the maximum number of IGMP snooping forwarding entries:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Set the maximum number of IGMP snooping forwarding entries.	entry-limit limit	The default setting is 4294967295.

Setting the IGMP last member query interval

A receiver host starts a report delay timer for a multicast group when it receives an IGMP group-specific query for the group. This timer is set to a random value in the range of 0 to the maximum response time advertised in the query. When the timer value decreases to 0, the host sends an IGMP report to the group.

The IGMP last member query interval defines the maximum response time advertised in IGMP group-specific queries. Set an appropriate value for the IGMP last member query interval to speed up hosts' responses to IGMP group-specific queries and avoid IGMP report traffic bursts.

Configuration restrictions and guidelines

When you set the IGMP last member query interval, follow these restrictions and guidelines:

· The Layer 2 device does not send an IGMP group-specific query if it receives an IGMP leave message from a port enabled with fast-leave processing.

· You can set the IGMP last member query interval globally for all VLANs in IGMP-snooping view or for a VLAN in VLAN view. For a VLAN, the VLAN-specific configuration takes priority over the global configuration.

Setting the IGMP last member query interval globally

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Set the IGMP last member query interval globally.	last-member-query-interval interval	The default setting is 1 second.

Setting the IGMP last member query interval in a VLAN

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Set the IGMP last member query interval for the VLAN.	igmp-snooping last-member-query-interval interval	The default setting is 1 second.

Configuring IGMP snooping port features

Before you configure IGMP snooping port features, complete the following tasks:

· Enable IGMP snooping for the VLAN.

· Determine the aging timer for dynamic router ports.

· Determine the aging timer for dynamic member ports.

· Determine the addresses of the multicast group and multicast source.

Setting aging timers for dynamic ports

When you set aging timers for dynamic ports, follow these restrictions and guidelines:

· If the memberships of multicast groups frequently change, you can set a relatively small value for the aging timer of the dynamic member ports. If the memberships of multicast groups rarely change, you can set a relatively large value.

· IGMP group-specific queries originated by the Layer 2 device trigger the adjustment of aging timers for dynamic member ports. If a dynamic member port receives such a query, its aging timer is set to twice the IGMP last member query interval. For more information about setting the IGMP last member query interval on the Layer 2 device, see "Setting the IGMP last member query interval."

· You can set the timers globally for all VLANs in IGMP-snooping view or for a VLAN in VLAN view. For a VLAN, the VLAN-specific configuration takes priority over the global configuration.

Setting the aging timers for dynamic ports globally

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Set the aging timer for dynamic router ports globally.	router-aging-time interval	The default setting is 260 seconds.
4. Set the global aging timer for dynamic member ports globally.	host-aging-time interval	The default setting is 260 seconds.

Setting the aging timers for dynamic ports in a VLAN

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Set the aging timer for dynamic router ports in the VLAN.	igmp-snooping router-aging-time interval	The default setting is 260 seconds.
4. Set the aging timer for dynamic member ports in the VLAN.	igmp-snooping host-aging-time interval	The default setting is 260 seconds.

Configuring static ports

You can configure the following types of static ports:

· Static member port—When you configure a port as a static member port for a multicast group, all hosts attached to the port will receive multicast data for the group.

The static member port does not respond to IGMP queries. When you complete or cancel this configuration on a port, the port does not send an unsolicited IGMP report or leave message.

· Static router port—When you configure a port as a static router port for a multicast group, all multicast data for the group received on the port will be forwarded.

To configure static ports:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Configure the port as a static port.	· Configure the port as a static member port: igmp-snooping static-group group-address [ source-ip source-address ] vlan vlan-id · Configure the port as a static router port: igmp-snooping static-router-port vlan vlan-id	By default, a port is not a static member port or a static router port.

Configuring a port as a simulated member host

When a port is configured as a simulated member host, it is equivalent to an independent host in the following ways:

· It sends an unsolicited IGMP report when you complete the configuration.

· It responds to IGMP general queries with IGMP reports.

· It sends an IGMP leave message when you cancel the configuration.

The version of IGMP running on the simulated member host is the same as the version of IGMP snooping running on the port. The port ages out in the same way as a dynamic member port.

To configure a port as a simulated member host:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Configure the port as a simulated member host.	igmp-snooping host-join group-address [ source-ip source-address ] vlan vlan-id	By default, the port is not a simulated member host.

Enabling fast-leave processing

This feature enables the device to immediately remove a port from the forwarding entry for a multicast group when the port receives a leave massage.

Configuration restrictions and guidelines

When you enable fast-leave processing, follow these restrictions and guidelines:

· Do not enable fast-leave processing on a port that has multiple receiver hosts in a VLAN. If fast-leave processing is enabled, after a receiver host leaves a multicast group, the other receivers cannot receive multicast data for the group.

· You can enable fast-leave processing globally for all ports in IGMP-snooping view or for a port in interface view. For a port, the port-specific configuration takes priority over the global configuration.

Configuration procedure

To enable fast-leave processing globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Enable fast-leave processing globally.	fast-leave [ vlan vlan-list ]	By default, fast-leave processing is disabled.

To enable fast-leave processing on a port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Enable fast-leave processing on the port.	igmp-snooping fast-leave [ vlan vlan-list ]	By default, fast-leave processing is disabled.

Disabling a port from becoming a dynamic router port

A receiver host might send IGMP general queries for testing purposes. On the Layer 2 device, the port that receives the messages becomes a dynamic router port. Before the aging timer for the port expires, the following problems might occur:

· All multicast data for the VLAN to which the port belongs flows to the port. Then, the port forwards the data to attached receiver hosts. The receiver hosts will receive unexpected multicast data.

· The port forwards the IGMP general queries to its upstream multicast routers. These messages might affect the multicast routing protocol state (such as the IGMP querier or DR election) on the multicast routers. This might further cause network interruption.

To solve these problems, you can disable a port from becoming a dynamic router port. This also improves network security and the control over receiver hosts.

To disable a port from becoming a dynamic router port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Disable the port from becoming a dynamic router port.	igmp-snooping router-port-deny [ vlan vlan-list ]	By default, a port can become a dynamic router port. This configuration does not affect the static router port configuration.

Configuring the IGMP snooping querier

This section describes how to configure an IGMP snooping querier.

Configuration prerequisites

Before you configure the IGMP snooping querier, complete the following tasks:

· Enable IGMP snooping for the VLAN.

· Determine the IGMP general query interval.

· Determine the maximum response time for IGMP general queries.

Enabling the IGMP snooping querier

This feature enables the device to periodically send IGMP general queries to establish and maintain multicast forwarding entries at the data link Layer. You can configure an IGMP snooping querier on a network without Layer 3 multicast devices.

Do not enable the IGMP snooping querier on a network that runs IGMP. An IGMP snooping querier does not take part in IGMP querier elections. However, it might affect IGMP querier elections if it sends IGMP general queries with a low source IP address.

To enable the IGMP snooping querier:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Enable the IGMP snooping querier.	igmp-snooping querier	By default, the IGMP snooping querier is disabled.

Configuring parameters for IGMP general queries and responses

CAUTION:

To avoid mistakenly delete multicast group members, make sure the IGMP general query interval is greater than the maximum response time for IGMP general queries.

You can modify the IGMP general query interval based on the actual condition of the network.

A receiver host starts a report delay timer for each multicast group that it has joined when it receives an IGMP general query. This timer is set to a random value in the range of 0 to the maximum response time advertised in the query. When the timer value decreases to 0, the host sends an IGMP report to the corresponding multicast group.

Set an appropriate value for the maximum response time for IGMP general queries to speed up hosts' responses to IGMP general queries and avoid IGMP report traffic bursts.

You can set the maximum response time for IGMP general queries globally for all VLANs in IGMP-snooping view or for a VLAN in VLAN view. For a VLAN, the VLAN-specific configuration takes priority over the global configuration.

Configuring parameters for IGMP general queries and responses globally

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Set the maximum response time for IGMP general queries.	max-response-time interval	The default setting is 10 seconds.
4. Set the IGMP last member query interval.	last-member-query-interval interval	The default setting is 1 second.

Configuring parameters for IGMP general queries and responses in a VLAN

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Set the IGMP general query interval in the VLAN.	igmp-snooping query-interval interval	The default setting is 125 seconds.
4. Set the maximum response time for IGMP general queries in the VLAN.	igmp-snooping max-response-time interval	The default setting is 10 seconds.

Configuring parameters for IGMP messages

This section describes how to configure parameters for IGMP messages.

Configuration prerequisites

Before you configure parameters for IGMP messages, complete the following tasks:

· Enable IGMP snooping for the VLAN.

· Determine the source IP address of IGMP general queries.

· Determine the source IP address of IGMP group-specific queries.

· Determine the source IP address of IGMP reports.

· Determine the source IP address of IGMP leave messages.

· Determine the 802.1p priority of IGMP messages.

Configuring source IP addresses for IGMP messages

The IGMP snooping querier might send IGMP general queries with the source IP address 0.0.0.0. The port that receives such queries will not be maintained as a dynamic router port. This might prevent the associated dynamic IGMP snooping forwarding entry from being correctly created at the data link layer and eventually cause multicast traffic forwarding failures.

To avoid this problem, you can configure a non-all-zero IP address as the source IP address of the IGMP queries on the IGMP snooping querier. This configuration might affect the IGMP querier election within the subnet.

You can also change the source IP address of IGMP reports or leave messages sent by a simulated member host or an IGMP snooping proxy.

To configure source IP addresses for IGMP messages:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Configure the source IP address for IGMP general queries.	igmp-snooping general-query source-ip ip-address	By default, the source IP address of IGMP general queries is the IP address of the current VLAN interface. If the current VLAN interface does not have an IP address, the source IP address is 0.0.0.0.
4. Configure the source IP address for IGMP group-specific queries.	igmp-snooping special-query source-ip ip-address	By default, the source IP address of IGMP group-specific queries is one of the following: · The source address of IGMP group-specific queries if the IGMP snooping querier of the VLAN has received IGMP general queries. · The IP address of the current VLAN interface if the IGMP snooping querier does not receive an IGMP general query. · 0.0.0.0 if the IGMP snooping querier does not receive an IGMP general query and the current VLAN interface does not have an IP address.
5. Configure the source IP address for IGMP reports.	igmp-snooping report source-ip ip-address	By default, the source IP address of IGMP reports is the IP address of the current VLAN interface. If the current VLAN interface does not have an IP address, the source IP address is 0.0.0.0.
6. Configure the source IP address for IGMP leave messages.	igmp-snooping leave source-ip ip-address	By default, the source IP address of IGMP leave messages is the IP address of the current VLAN interface. If the current VLAN interface does not have an IP address, the source IP address is 0.0.0.0.

Setting the 802.1p priority for IGMP messages

When congestion occurs on outgoing ports of the Layer 2 device, it forwards IGMP messages in their 802.1p priority order, from highest to lowest. You can assign a higher 802.1p priority to IGMP messages that are created or forwarded by the device.

You can set the 802.1p priority globally for all VLANs in IGMP-snooping view or for a VLAN in VLAN view. For a VLAN, the VLAN-specific configuration takes priority over the global configuration.

Setting the 802.1p priority for IGMP messages globally

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Set the 802.1p priority for IGMP messages.	dot1p-priority priority-number	The default setting is 0.

Setting the 802.1p priority for IGMP messages in a VLAN

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Set the 802.1p priority for IGMP messages in the VLAN.	igmp-snooping dot1p-priority priority-number	The default setting is 0.

Configuring IGMP snooping policies

Before you configure IGMP snooping policies, complete the following tasks:

· Enable IGMP snooping for the VLAN.

· Determine the ACL used by the multicast group policy.

· Determine the maximum number of multicast groups that a port can join.

Configuring a multicast group policy

This feature enables the device to filter IGMP reports by using an ACL that specifies the multicast groups and the optional sources. It is used to control the multicast groups that hosts can join.

Configuration restrictions and guidelines

When you configure a multicast group policy, follow these restrictions and guidelines:

· This configuration takes effect only on the multicast groups that ports join dynamically.

· You can configure a multicast group policy globally for all ports in IGMP-snooping view or for a port in interface view. For a port, the port-specific configuration takes priority over the global configuration.

Configuration procedure

To configure a multicast group policy globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Configure a multicast group policy globally.	group-policy acl-number [ vlan vlan-list ]	By default, no multicast group policies exist. Hosts can join any multicast groups.

To configure a multicast group policy on a port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Configure a multicast group policy on the port.	igmp-snooping group-policy acl-number [ vlan vlan-list ]	By default, no multicast group policies exist on a port. Hosts attached to the port can join any multicast groups.

Enabling dropping unknown multicast data

This feature enables the device to drop all unknown multicast data. Unknown multicast data refers to multicast data for which no forwarding entries exist in the IGMP snooping forwarding table.

If you do not enable this feature, the unknown multicast data is flooded in the VLAN to which the data belongs.

Configuration restrictions and guidelines

When you enable dropping unknown multicast data, follow these restrictions and guidelines:

· You can enable dropping unknown multicast data globally for all VLANs in IGMP-snooping view or for a VLAN in VLAN view. The drop-unknown command in IGMP-snooping view and the igmp-snooping drop-unknown command in VLAN view are mutually exclusive. You cannot configure them on the same device.

· For a VLAN enabled with this feature, some device models drop unknown IPv6 multicast data for the VLAN.

· For a VLAN enabled with this feature, some device models still forward unknown IPv4 multicast data for the VLAN to other router ports in the VLAN.

Configuration procedure

To enable dropping unknown multicast data globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Enable dropping unknown multicast data globally.	drop-unknown	By default, dropping unknown multicast data is disabled. Unknown multicast data is flooded.

To enable dropping unknown multicast data for a VLAN:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Enable dropping unknown multicast data for the VLAN.	igmp-snooping drop-unknown	By default, dropping unknown multicast data is disabled. Unknown multicast data is flooded.

Enabling IGMP report suppression

This feature enables the device to forward only the first IGMP report for a multicast group to its directly connected Layer 3 device. Other reports for the same group in the same query interval are discarded. This reduces the multicast traffic.

To enable IGMP report suppression:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Enable IGMP report suppression.	report-aggregation	By default, IGMP report suppression is enabled.

Setting the maximum number of multicast groups on a port

You can set the maximum number of multicast groups on a port to regulate the port traffic.

Configuration restrictions and guidelines

When you set the maximum number of multicast groups on a port, follow these restrictions and guidelines:

· This configuration takes effect only on the multicast groups that a port joins dynamically.

· If the number of multicast groups on a port exceeds the limit, the system removes all the forwarding entries related to that port. The receiver hosts attached to that port can join multicast groups again before the number of multicast groups on the port reaches the limit.

Configuration procedure

To set the maximum number of multicast groups on a port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Set the maximum number of multicast groups on a port.	igmp-snooping group-limit limit [ vlan vlan-list ]	The default setting is 4294967295.

Enabling the multicast group replacement feature

This feature enables the device to replace an existing group with a newly joined group when the number of groups exceeds the upper limit. This feature is typically used in the channel switching application. Without this feature, the Layer 2 device discards IGMP reports for new groups, and the user cannot change to the new channel.

Configuration restrictions and guidelines

When you enable the multicast group replacement feature, follow these restrictions and guidelines:

· This configuration takes effect only on the multicast groups that a port joins dynamically.

· You can enable this feature globally for all ports in IGMP-snooping view or for a port in interface view. For a port, the port-specific configuration takes priority over the global configuration.

Configuration procedure

To enable the multicast group replacement feature globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP-snooping view.	igmp-snooping	N/A
3. Enable the multicast group replacement feature globally.	overflow-replace [ vlan vlan-list ]	By default, the multicast group replacement feature is disabled.

To enable the multicast group replacement feature on a port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Enable multicast group replacement feature on a port.	igmp-snooping overflow-replace [ vlan vlan-list ]	By default, the multicast group replacement feature is disabled.

Displaying and maintaining IGMP snooping

Execute display commands in any view and reset commands in user view.

Task	Command
Display IGMP snooping status.	display igmp-snooping [ global \| vlan vlan-id ]
Display dynamic IGMP snooping group entries.	display igmp-snooping group [ group-address \| source-address ] * [ vlan vlan-id ] [ verbose ] [ slot slot-number ]
Display dynamic router port information.	display igmp-snooping router-port [ vlan vlan-id ] [ slot slot-number ]
Display static IGMP snooping group entries.	display igmp-snooping static-group [ group-address \| source-address ] * [ vlan vlan-id ] [ verbose ] [ slot slot-number ]
Display static router port information.	display igmp-snooping static-router-port [ vlan vlan-id ] [ slot slot-number ]
Display statistics for the IGMP messages learned by IGMP snooping.	display igmp-snooping statistics
Display information about Layer 2 IP multicast groups.	display l2-multicast ip [ group group-address \| source source-address ] * [ vlan vlan-id ] [ slot slot-number ]
Display Layer 2 IP multicast group entries.	display l2-multicast ip forwarding [ group group-address \| source source-address ] * [ vlan vlan-id ] [ slot slot-number ]
Display information about Layer 2 MAC multicast groups.	display l2-multicast mac [ mac-address ] [ vlan vlan-id ] [ slot slot-number ]
Display Layer 2 MAC multicast group entries.	display l2-multicast mac forwarding [ mac-address ] [ vlan vlan-id ] [ slot slot-number ]
Clear dynamic IGMP snooping group entries.	reset igmp-snooping group { group-address [ source-address ] \| all } [ vlan vlan-id ]
Clear dynamic router port information.	reset igmp-snooping router-port { all \| vlan vlan-id }
Clear statistics for IGMP messages learned through IGMP snooping.	reset igmp-snooping statistics

IGMP snooping configuration example

Network requirements

As shown in Figure 12:

· The source sends multicast traffic to multicast group 224.1.1.1.

· The client is a receiver host of the multicast group.

· The route between the source and the client is reachable.

Configure the AC so that the client can receive the multicast traffic from the source.

Figure 12 Network diagram

Configuration procedure

Configuring Router A

# Enable IP multicast routing globally, and enable PIM-DM and IGMP on the port that connects to the AC. (Details not shown.)

Configuring the AC

1. Configure WLAN services:

# Create VLAN 100.

<AC> system-view

[AC] vlan 100

[AC-vlan100] quit

# Create service template 1, and set the SSID to Multicast for the service template.

[AC] wlan service-template 1

[AC-wlan-st-1] ssid Multicast

# Bind VLAN 100 to service template 1, and enable the service template.

[AC-wlan-st-1] vlan 100

[AC-wlan-st-1] service-template enable

[AC-wlan-st-1] quit

# Create an AP named ap with model WA536-WW, and set the serial ID of the AP to 219801A1NQB117012935.

[AC] wlan ap ap model WA536-WW

[AC-wlan-ap-ap] serial-id 219801A1NQB117012935

# Bind service template 1 to radio 1, and enable radio 1 for AP ap.

[AC-wlan-ap-ap] radio 1

[AC-wlan-ap-ap-radio-1] service-template 1

[AC-wlan-ap-ap-radio-1] radio enable

[AC-wlan-ap-ap-radio-1] quit

[AC-wlan-ap-ap]quit

2. Configure IGMP snooping:

# Enable IGMP snooping globally.

[AC] igmp-snooping

[AC-igmp-snooping] quit

# In VLAN 100, enable IGMP snooping, and specify IGMP snooping version 3.

[AC] vlan 100

[AC-vlan100] igmp-snooping enable

[AC-vlan100] igmp-snooping version 3

[AC-vlan100] quit

3. Configure Ethernet interfaces.

# Configure GigabitEthernet 1/0/2 on the access controller as a trunk port, and assign the port to VLAN 100.

[AC] interface GigabitEthernet 1/0/2

[AC-GigabitEthernet1/0/2] port link-type trunk

[AC-GigabitEthernet1/0/2] port trunk permit vlan 100

[AC-GigabitEthernet1/0/2] quit

Configuring the client

# Configure the client to access the WLAN service with the SSID Multicast and request multicast traffic for multicast group 224.1.1.1. (Details not shown.)

Verifying the configuration

# Display detailed information about dynamic IGMP snooping group entries for VLAN 100 on the AC.

[AC] display igmp-snooping group vlan 100 verbose

Total 1 entries.

VLAN 100: Total 1 entries.

(0.0.0.0, 224.1.1.1)

Attribute: local port

FSM information: normal

Host slots (0 in total):

Host ports (1 in total):

WLAN-BSS1/0/20 (00:03:23)

The output shows that WLAN-BSS 1/0/20 on the AC has joined multicast group 224.1.1.1.

Troubleshooting IGMP snooping

Layer 2 multicast forwarding cannot function

Symptom

Layer 2 multicast forwarding cannot function on the Layer 2 device.

Solution

To resolve the problem:

1. Use the display igmp-snooping command to display IGMP snooping status.

2. If IGMP snooping is not enabled, use the igmp-snooping command in system view to enable IGMP snooping globally. Then, use the igmp-snooping enable command in VLAN view to enable IGMP snooping for the VLAN.

3. If IGMP snooping is enabled globally but not enabled for the VLAN, use the igmp-snooping enable command in VLAN view to enable IGMP snooping for the VLAN.

4. If the problem persists, contact H3C Support.

Multicast group policy does not work

Symptom

Hosts can receive multicast data from multicast groups that are not permitted by the multicast group policy.

Solution

To resolve the problem:

1. Use the display acl command to verify that the configured ACL meets the multicast group policy requirements.

2. Use the display this command in IGMP-snooping view or in a corresponding interface view to verify that the correct multicast group policy has been applied. If the applied multicast group policy is not correct, use the group-policy or igmp-snooping group-policy command to apply the correct multicast group policy.

3. Use the display igmp-snooping command to verify that dropping unknown multicast data is enabled. If dropping unknown multicast data is not enabled, use the drop-unknown or igmp-snooping drop-unknown command to enable dropping unknown multicast data.

4. If the problem persists, contact H3C Support.

Configuring MLD snooping

Overview

MLD snooping runs on a Layer 2 device as an IPv6 multicast constraining mechanism to improve multicast forwarding efficiency. It creates Layer 2 multicast forwarding entries from MLD messages that are exchanged between the hosts and the router.

As shown in Figure 13, when MLD snooping is not enabled, the AC floods IPv6 multicast packets to all hosts in a VLAN. When MLD snooping is enabled, the AC forwards multicast packets of known IPv6 multicast groups only to the receivers.

Figure 13 Multicast packet transmission processes without and with MLD snooping

MLD snooping ports

As shown in Figure 14, MLD snooping runs on Device A and Device B, and Host A and Host C are receiver hosts in an IPv6 multicast group. MLD snooping ports are divided into member ports and router ports.

Figure 14 MLD snooping ports

Router ports

On an MLD snooping Layer 2 device, the ports toward Layer 3 multicast devices are called router ports. In Figure 14, GigabitEthernet 1/0/1 of Device A and GigabitEthernet 1/0/1 of Device B are router ports.

Router ports contain the following types:

· Dynamic router port—When a port receives an MLD general query whose source address is not 0::0, the port is added into the dynamic router port list. At the same time, an aging timer is started for the port. If the port receives an MLD general query before the timer expires, the timer is reset. If the port does not receive an MLD general query when the timer expires, the port is removed from the dynamic router port list.

Do not confuse the "router port" in MLD snooping with the "routed interface" commonly known as the "Layer 3 interface." The router port in MLD snooping is a Layer 2 interface.

Member ports

On an MLD snooping Layer 2 device, the ports toward receiver hosts are called member ports. In Figure 14, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 of Device A and GigabitEthernet 1/0/2 of Device B are member ports.

Member ports contain the following types:

· Dynamic member port—When a port receives an MLD report, it is added to the associated dynamic MLD snooping forwarding entry as an outgoing interface. At the same time, an aging timer is started for the port. If the port receives an MLD report before the timer expires, the timer is reset. If the port does not receive an MLD report when the timer expires, the port is removed from the associated dynamic forwarding entry.

· Static member port—When a port is statically configured as a member port, it is added to the associated static MLD snooping forwarding entry as an outgoing interface. The static member port does not age out, and it can be deleted only manually.

Unless otherwise specified, router ports and member ports in this document include both static and dynamic router ports and member ports.

How MLD snooping works

The ports in this section are dynamic ports. For information about how to configure and remove static ports, see "Configuring static ports."

MLD messages include general query, MLD report, and done message. An MLD snooping-enabled device performs differently depending on the MLD message types.

General query

The MLD querier periodically sends MLD general queries to all hosts and routers on the local subnet to check for the existence of IPv6 multicast group members.

After receiving an MLD general query, the Layer 2 device forwards the query to all ports in the VLAN except the receiving port. The Layer 2 device also performs one of the following actions:

· If the receiving port is a dynamic router port in the dynamic router port list, the Layer 2 device restarts the aging timer for the router port.

· If the receiving port does not exist in the dynamic router port list, the Layer 2 device adds the port to the dynamic router port list. It also starts an aging timer for the port.

MLD report

A host sends an MLD report to the MLD querier for the following purposes:

· Responds to queries if the host is an IPv6 multicast group member.

· Applies for an IPv6 multicast group membership.

After receiving an MLD report from a host, the Layer 2 device forwards the report through all the router ports in the VLAN. It also resolves the IPv6 address of the reported IPv6 multicast group, and looks up the forwarding table for a matching entry as follows:

· If no match is found, the Layer 2 device creates a forwarding entry for the group with the receiving port an outgoing interface. It also marks the receiving port as a dynamic member port and starts an aging timer for the port.

· If a match is found but the matching forwarding entry does not contain the receiving port, the Layer 2 device adds the receiving port to the outgoing interface list. It also marks the port as a dynamic member port to the forwarding entry and starts an aging timer for the port.

· If a match is found and the matching forwarding entry contains the receiving port, the Layer 2 device restarts the aging timer for the port.

In an application with an IPv6 multicast group policy configured on an MLD snooping-enabled Layer 2 device, when a user requests a multicast program, the user's host initiates an MLD report. After receiving this report message, the Layer 2 device resolves the IPv6 multicast group address in the report and performs ACL filtering on the report. If the report passes ACL filtering, the Layer 2 device creates an MLD snooping forwarding entry for the group with the receiving port as an outgoing interface. Otherwise, the Layer 2 device drops this report message, in which case, the IPv6 multicast data for the IPv6 multicast group is not sent to this port, and the user cannot retrieve the program.

A Layer 2 device does not forward an MLD report through a non-router port because of the host MLD report suppression mechanism.

Done message

When a host leaves an IPv6 multicast group, the host sends an MLD done message to the Layer 3 devices. When the Layer 2 device receives the MLD done message on a dynamic member port, the Layer 2 device first examines whether a forwarding entry matches the IPv6 multicast group address in the message.

· If no match is found, the Layer 2 device discards the MLD done message.

· If a match is found but the receiving port is not an outgoing interface in the forwarding entry, the Layer 2 device discards the MLD done message.

· If a match is found and the receiving port is not the only outgoing interface in the forwarding entry, the Layer 2 device performs the following actions:

? Discards the MLD done message.

? Sends an MLD multicast-address-specific query to identify whether the group has active listeners attached to the receiving port.

? Sets the aging timer for the receiving port to twice the MLD last listener query interval.

· If a match is found and the receiving port is the only outgoing interface in the forwarding entry, the Layer 2 device performs the following actions:

? Forwards the MLD done message to all router ports in the VLAN.

? Sends an MLD multicast-address-specific query to identify whether the group has active listeners attached to the receiving port.

? Sets the aging timer for the receiving port to twice the MLD last listener query interval.

After receiving the MLD done message on a port, the MLD querier resolves the IPv6 multicast group address in the message. Then, it sends an MLD multicast-address-specific query to the IPv6 multicast group through the receiving port.

After receiving the MLD multicast-address-specific query, the Layer 2 device forwards the query through all its router ports in the VLAN and all member ports of the IPv6 multicast group. Then, it waits for the responding MLD report from the directly connected hosts. For the dynamic member port that received the done message, the Layer 2 device also performs one of the following actions:

· If the port receives an MLD report before the aging timer expires, the Layer 2 device resets the aging timer for the port.

· If the port does not receive any MLD report messages when the aging timer expires, the Layer 2 device removes the port from the forwarding entry for the IPv6 multicast group.

Protocols and standards

RFC 4541, Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches

Command and hardware compatibility

The WX1800H series access controllers do not support the slot keyword or the slot-number argument.

MLD snooping configuration task list

Tasks at a glance
Configuring basic MLD snooping features: · (Required.) Enabling MLD snooping · (Optional.) Specifying an MLD snooping version · (Optional.) Setting the maximum number of MLD snooping forwarding entries · (Optional.) Setting the MLD last listener query interval
(Optional.) Configuring MLD snooping port features: · Setting aging timers for dynamic ports · Configuring static ports · Configuring a port as a simulated member host · Enabling fast-leave processing · Disabling a port from becoming a dynamic router port
(Optional.) Configuring the MLD snooping querier: · Enabling the MLD snooping querier · Configuring parameters for MLD general queries and responses
(Optional.) Configuring parameters for MLD messages: · Configuring source IPv6 addresses for MLD messages · Setting the 802.1p priority for MLD messages
(Optional.) Configuring MLD snooping policies: · Configuring an IPv6 multicast group policy · Enabling dropping unknown IPv6 multicast data · Enabling MLD report suppression · Setting the maximum number of IPv6 multicast groups on a port · Enabling the IPv6 multicast group replacement feature

Tasks at a glance

Configuring basic MLD snooping features:

· (Required.) Enabling MLD snooping

· (Optional.) Specifying an MLD snooping version

· (Optional.) Setting the maximum number of MLD snooping forwarding entries

· (Optional.) Setting the MLD last listener query interval

(Optional.) Configuring MLD snooping port features:

· Setting aging timers for dynamic ports

· Configuring static ports

· Configuring a port as a simulated member host

· Enabling fast-leave processing

· Disabling a port from becoming a dynamic router port

(Optional.) Configuring the MLD snooping querier:

· Enabling the MLD snooping querier

· Configuring parameters for MLD general queries and responses

(Optional.) Configuring parameters for MLD messages:

· Configuring source IPv6 addresses for MLD messages

· Setting the 802.1p priority for MLD messages

(Optional.) Configuring MLD snooping policies:

· Configuring an IPv6 multicast group policy

· Enabling dropping unknown IPv6 multicast data

· Enabling MLD report suppression

· Setting the maximum number of IPv6 multicast groups on a port

· Enabling the IPv6 multicast group replacement feature

The MLD snooping configurations made on Layer 2 aggregate interfaces do not interfere with the configurations made on member ports. In addition, the configurations made on Layer 2 aggregate interfaces do not take part in aggregation calculations. The configuration made on a member port of the aggregate group takes effect after the port leaves the aggregate group.

Configuring basic MLD snooping features

Before you configure basic MLD snooping features, complete the following tasks:

· Configure VLANs.

· Determine the MLD snooping version.

· Determine the MLD last listener query interval.

· Determine the maximum number of MLD snooping forwarding entries.

· Determine the MLD last listener query interval.

Enabling MLD snooping

When you enable MLD snooping, follow these restrictions and guidelines:

· You must enable MLD snooping globally before you can enable it for a VLAN.

· MLD snooping configuration made in VLAN view takes effect only on the member ports in that VLAN.

· You can enable MLD snooping for the specified VLANs in MLD-snooping view or for a VLAN in VLAN view. For a VLAN, the configuration in VLAN interface has the same priority as the configuration in MLD-snooping view, and the most recent configuration takes effect.

To enable MLD snooping for the specified VLANs:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable MLD snooping globally and enter MLD-snooping view.	mld-snooping	By default, MLD snooping is globally disabled.
3. Enable MLD snooping for the specified VLANs.	enable vlan vlan-list	By default, MLD snooping is disabled for a VLAN.

To enable MLD snooping for a VLAN:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable MLD snooping globally and enter MLD-snooping view.	mld-snooping	By default, MLD snooping is globally disabled.
3. Return to system view.	quit	N/A
4. Enter VLAN view.	vlan vlan-id	N/A
5. Enable MLD snooping for the VLAN.	mld-snooping enable	By default, MLD snooping is disabled in a VLAN.

Specifying an MLD snooping version

Different MLD snooping versions can process different versions of MLD messages:

· MLDv1 snooping can process MLDv1 messages, but it floods MLDv2 messages in the VLAN instead of processing them.

· MLDv2 snooping can process MLDv1 and MLDv2 messages.

If you change MLDv2 snooping to MLDv1 snooping, the system does the following:

· Clears all MLD snooping forwarding entries that are dynamically created.

· Keeps static MLDv2 snooping forwarding entries (*, G).

· Clears static MLDv2 snooping forwarding entries (S, G), which will be restored when MLD snooping is switched back to MLDv2 snooping.

For more information about static MLD snooping forwarding entries, see "Configuring static ports."

You can specify the version for the specified VLANs in MLD-snooping view or for a VLAN in VLAN view. For a VLAN, the configuration in VLAN view has the same priority as the configuration in MLD-snooping view, and the most recent configuration takes effect.

To specify an MLD snooping version for the specified VLANs:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable MLD snooping globally and enter MLD-snooping view.	mld-snooping	N/A
3. Specify an MLD snooping version for the specified VLANs.	version version-number vlan vlan-list	The default setting is 1.

To specify an MLD snooping version for a VLAN:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Specify an MLD snooping version for the VLAN.	mld-snooping version version-number	The default setting is 1.

Setting the maximum number of MLD snooping forwarding entries

You can modify the maximum number of MLD snooping forwarding entries, including dynamic entries and static entries. When the number of forwarding entries on the device reaches the upper limit, the device does not automatically remove any existing entries. To allow new entries to be created, H3C recommends that you manually remove some entries.

To set the maximum number of MLD snooping forwarding entries:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Set the maximum number of MLD snooping forwarding entries.	entry-limit limit	The default setting is 4294967295.

Setting the MLD last listener query interval

A receiver host starts a report delay timer for an IPv6 multicast group when it receives an MLD multicast-address-specific query for the group. This timer is set to a random value in the range of 0 to the maximum response time advertised in the query. When the timer value decreases to 0, the host sends an MLD report to the group.

The MLD last listener query interval defines the maximum response time advertised in MLD multicast-address-specific queries. Set an appropriate value for the MLD last listener query interval to speed up hosts' responses to MLD multicast-address-specific queries and avoid MLD report traffic bursts.

Configuration restrictions and guidelines

When you set the MLD last listener query interval, follow these restrictions and guidelines:

· The Layer 2 device does not send an MLD multicast-address-specific query if it receives an MLD done message from a port enabled with fast-leave processing.

· You can set the MLD last listener query interval globally for all VLANs in MLD-snooping view or for a VLAN in VLAN view. For a VLAN, the VLAN-specific configuration takes priority over the global configuration.

Setting the MLD last listener query interval globally

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Set the MLD last listener query interval globally.	last-listener-query-interval interval	The default setting is 1 second.

Setting the MLD last listener query interval in a VLAN

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Set the MLD last listener query interval in the VLAN.	mld-snooping last-listener-query-interval interval	The default setting is 1 second.

Configuring MLD snooping port features

Before you configure MLD snooping port features, complete the following tasks:

· Enable MLD snooping for the VLAN.

· Determine the aging timer for dynamic router ports.

· Determine the aging timer for dynamic member ports.

· Determine the addresses of the IPv6 multicast group and IPv6 multicast source.

Setting aging timers for dynamic ports

When you set aging timers for dynamic ports, follow these restrictions and guidelines:

· If the memberships of IPv6 multicast groups frequently change, set a relatively small value for the aging timer of the dynamic member ports. If the memberships of IPv6 multicast groups rarely change, you can set a relatively large value.

· MLD multicast-address-specific queries originated by the Layer 2 device trigger the adjustment of aging timers of dynamic member ports. If a dynamic member port receives such a query, its aging timer is set to twice the MLD last listener query interval. For more information about setting the MLD last listener query interval on the Layer 2 device, see "Setting the MLD last listener query interval."

· You can set the timers globally for all VLANs in MLD-snooping view or for a VLAN in VLAN view. For a VLAN, the VLAN-specific configuration takes priority over the global configuration.

Setting the aging timers for dynamic ports globally

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Set the aging timer for dynamic router ports globally.	router-aging-time interval	The default setting is 260 seconds.
4. Set the aging timer for dynamic member ports globally.	host-aging-time interval	The default setting is 260 seconds.

Setting the aging timers for dynamic ports in a VLAN

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Set the aging timer for dynamic router ports in the VLAN.	mld-snooping router-aging-time interval	The default setting is 260 seconds.
4. Set the aging timer for dynamic member ports in the VLAN.	mld-snooping host-aging-time interval	The default setting is 260 seconds.

Configuring static ports

You can configure the following types of static ports:

· Static member port—When you configure a port as a static member port for an IPv6 multicast group, all hosts attached to the port will receive IPv6 multicast data for the group.

The static member port does not respond to MLD queries. When you complete or cancel this configuration, the port does not send an unsolicited report or done message.

· Static router port—When you configure a port as a static router port for an IPv6 multicast group, all IPv6 multicast data for the group received on the port will be forwarded.

To configure static ports:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Configure the port as a static port.	· Configure the port as a static member port: mld-snooping static-group ipv6-group-address [ source-ip ipv6-source-address ] vlan vlan-id · Configure the port as a static router port: mld-snooping static-router-port vlan vlan-id	By default, a port is not a static member port or a static router port.

Configuring a port as a simulated member host

When a port is configured as a simulated member host, it is equivalent to an independent host in the following ways:

· It sends an unsolicited MLD report when you complete the configuration.

· It responds to MLD general queries with MLD reports.

· It sends an MLD done message when you remove the configuration.

The version of MLD running on the simulated member host is the same as the version of MLD snooping running on the port. The port ages out in the same ways as a dynamic member port.

To configure a port as a simulated member host:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Configure the port as a simulated member host.	mld-snooping host-join ipv6-group-address [ source-ip ipv6-source-address ] vlan vlan-id	By default, the port is not a simulated member host.

Enabling fast-leave processing

This feature enables the device to immediately remove a port from the forwarding entry for an IPv6 multicast group when the port receives a done message.

Configuration restrictions and guidelines

When you enable fast-leave processing, follow these restrictions and guidelines:

· Do not enable fast-leave processing on a port that have multiple receiver hosts attached in a VLAN. If fast-leave processing is enabled, after a receiver host leaves an IPv6 multicast group, the other receivers cannot receive IPv6 multicast data for the group.

· You can enable fast-leave processing globally for all ports in MLD-snooping view or for a port in interface view. For a port, the port-specific configuration takes priority over the global configuration.

Configuration procedure

To enable fast-leave processing globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Enable fast-leave processing globally.	fast-leave [ vlan vlan-list ]	By default, fast-leave processing is disabled.

To enable fast-leave processing on a port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Enable fast-leave processing on the port.	mld-snooping fast-leave [ vlan vlan-list ]	By default, fast-leave processing is disabled.

Disabling a port from becoming a dynamic router port

A receiver host might send MLD general queries for testing purposes. On the Layer 2 device, the port that receives the queries becomes a dynamic router port. Before the aging timer for the port expires, the following problems might occur:

· All IPv6 multicast data for the VLAN to which the port belongs flows to the port. Then, the port forwards the data to attached receiver hosts. The receiver hosts will receive unexpected IPv6 multicast data.

· The port forwards the MLD general queries to its upstream multicast routers. These messages might affect the multicast routing protocol state (such as the MLD querier or DR election) on the multicast routers. This might further cause network interruption.

To solve these problems, you can disable the router port from becoming a dynamic router port. This also improves network security and the control over receiver hosts.

To disable a port from becoming a dynamic router port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Disable the port from becoming a dynamic router port.	mld-snooping router-port-deny [ vlan vlan-list ]	By default, a port can become a dynamic router port. This configuration does not affect the static router port configuration.

Configuring the MLD snooping querier

This section describes how to configure the MLD snooping querier.

Configuration prerequisites

Before you configure the MLD snooping querier, complete the following tasks:

· Enable MLD snooping for the VLAN.

· Determine the MLD general query interval.

· Determine the maximum response time for MLD general queries.

Enabling the MLD snooping querier

This feature enables the device to periodically send MLD general queries to establish and maintain multicast forwarding entries at the data link Layer. You can configure an MLD snooping querier on a network without Layer 3 multicast devices.

Do not enable the MLD snooping querier on an IPv6 multicast network that runs MLD. An MLD snooping querier does not participate in MLD querier elections. However, it might affect MLD querier elections if it sends MLD general queries with a low source IPv6 address.

To enable the MLD snooping querier for a VLAN:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Enable the MLD snooping querier.	mld-snooping querier	By default, the MLD snooping querier is disabled.

Configuring parameters for MLD general queries and responses

CAUTION:

To avoid mistakenly delete IPv6 multicast group members, make sure the MLD general query interval is greater than the maximum response time for MLD general queries.

You can modify the MLD general query interval based on the actual network conditions.

A receiver host starts a report delay timer for each IPv6 multicast group that it has joined when it receives an MLD general query. This timer is set to a random value in the range of 0 to the maximum response time advertised in the query. When the timer value decreases to 0, the host sends an MLD report to the corresponding IPv6 multicast group.

Set an appropriate value for the maximum response time for MLD general queries to speed up hosts' responses to MLD general queries and avoid MLD report traffic bursts.

You can set the maximum response time for MLD general queries globally for all VLANs in MLD-snooping view or for a VLAN in VLAN view. For a VLAN, the VLAN-specific configuration takes priority over the global configuration.

Configuring parameters for MLD general queries and responses globally

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Set the maximum response time for MLD general queries.	max-response-time interval	The default setting is 10 seconds.

Configuring parameters for MLD general queries and responses in a VLAN

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Set the MLD general query interval in the VLAN.	mld-snooping query-interval interval	The default setting is 125 seconds.
4. Set the maximum response time for MLD general queries in the VLAN.	mld-snooping max-response-time interval	The default setting is 10 seconds.

Configuring parameters for MLD messages

This section describes how to configure parameters for MLD messages.

Configuration prerequisites

Before you configure parameters for MLD messages, complete the following tasks:

· Enable MLD snooping for the VLAN.

· Determine the source IPv6 address of MLD general queries.

· Determine the source IPv6 address of MLD multicast-address-specific queries.

· Determine the source IPv6 address of MLD reports.

· Determine the source IPv6 address of MLD done messages.

· Determine the 802.1p priority of MLD messages.

Configuring source IPv6 addresses for MLD messages

You can change the source IPv6 address of the MLD queries sent by an MLD snooping querier. This configuration might affect MLD querier election within the subnet.

You can also change the source IPv6 address of MLD reports or done messages sent by a simulated member host or an MLD snooping proxy.

To configure the source IP addresses for MLD messages in a VLAN:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Configure the source IPv6 address for MLD general queries.	mld-snooping general-query source-ip ipv6-address	By default, the source IPv6 address of MLD general queries is the IPv6 link-local address of the current VLAN interface. If the current VLAN interface does not have an IPv6 link-local address, the source IPv6 address is FE80::02FF:FFFF:FE00:0001.
4. Configure the source IPv6 address for MLD multicast-address-specific queries.	mld-snooping special-query source-ip ipv6-address	By default, the source IPv6 address of MLD multicast-address-specific queries is one of the following: · The source address of MLD general queries if the MLD snooping querier of the VLAN has received MLD general queries. · The IPv6 link-local address of the current VLAN interface if the MLD snooping querier does not receive an MLD general query. · FE80::02FF:FFFF:FE00:0001 if the MLD snooping querier does not receive an MLD general query and the current VLAN interface does not have an IPv6 link-local address.
5. Configure the source IPv6 address for MLD reports.	mld-snooping report source-ip ipv6-address	By default, the source IPv6 address of MLD reports is the IPv6 link-local address of the current VLAN interface. If the current VLAN interface does not have an IPv6 link-local address, the source IPv6 address is FE80::02FF:FFFF:FE00:0001.
6. Configure the source IPv6 address for MLD done messages.	mld-snooping done source-ip ipv6-address	By default, the source IPv6 address of MLD done messages is the IPv6 link-local address of the current VLAN interface. If the current VLAN interface does not have an IPv6 link-local address, the source IPv6 address is FE80::02FF:FFFF:FE00:0001.

Setting the 802.1p priority for MLD messages

When congestion occurs on outgoing ports of the Layer 2 device, it forwards MLD messages in their 802.1p priority order, from highest to lowest. You can assign a higher 802.1p priority to MLD messages that are created or forwarded by the device.

You can set the 802.1p priority globally for all VLANs in MLD-snooping view or for a VLAN in VLAN view. For a VLAN, the VLAN-specific configuration takes priority over the global configuration.

Setting the 802.1p priority for MLD messages globally

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Set the 802.1p priority for MLD messages.	dot1p-priority priority-number	The default setting is 0.

Setting the 802.1p priority for MLD messages in a VLAN

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Set the 802.1p priority for MLD messages in the VLAN.	mld-snooping dot1p-priority priority-number	The default setting is 0.

Configuring MLD snooping policies

Before you configure MLD snooping policies, complete the following tasks:

· Enable MLD snooping for the VLAN.

· Determine the ACL used by the IPv6 multicast group policy.

· Determine the maximum number of IPv6 multicast groups that a port can join.

Configuring an IPv6 multicast group policy

This feature enables the device to filter MLD reports by using an ACL that specifies the IPv6 multicast groups and the optional sources. It is used to control the IPv6 multicast groups that receiver hosts can join.

Configuration restrictions and guidelines

When you configure an IPv6 multicast group policy, follow these restrictions and guidelines:

· This configuration takes effect on the IPv6 multicast groups that ports join dynamically.

· You can configure an IPv6 multicast group policy globally for all ports in MLD-snooping view or for a port in interface view. For a port, the port-specific configuration takes priority over the global configuration.

Configuration procedure

To configure an IPv6 multicast group policy globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Configure an IPv6 multicast group policy globally.	group-policy acl6-number [ vlan vlan-list ]	By default, IPv6 multicast group policies are not configured. Receiver host can join any IPv6 multicast groups.

To configure an IPv6 multicast group policy on a port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Configure an IPv6 multicast group policy for the port.	mld-snooping group-policy acl6-number [ vlan vlan-list ]	By default, the port is not configured with an IPv6 multicast group policy. Receiver hosts attached to the port can join any IPv6 multicast groups.

Enabling dropping unknown IPv6 multicast data

This feature enables the device to drop all unknown IPv6 multicast data. Unknown IPv6 multicast data refers to IPv6 multicast data for which no forwarding entries exist in the MLD snooping forwarding table.

If you do not enable this feature, the unknown IPv6 multicast data is flooded in the VLAN to which the data belongs.

Configuration restrictions and guidelines

When you enable dropping unknown IPv6 multicast data, follow these restrictions and guidelines:

· You can enable this feature globally for all VLANs in MLD-snooping view or for a VLAN in VLAN view. The drop-unknown command in MLD-snooping view and the mld-snooping drop-unknown command in VLAN view are mutually exclusive. You cannot configure them on the same device.

· For a VLAN enabled with this feature, some device models drop unknown IPv4 multicast data for the VLAN.

· For a VLAN enabled with this feature, some device models still forward unknown IPv6 multicast data for the VLAN to other router ports in the VLAN.

Configuration procedure

To enable dropping unknown IPv6 multicast data globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Enable dropping unknown IPv6 multicast data globally.	drop-unknown	By default, this feature is disabled. Unknown IPv6 multicast data is flooded.

To enable dropping unknown IPv6 multicast data for a VLAN:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter VLAN view.	vlan vlan-id	N/A
3. Enable dropping unknown IPv6 multicast data for the VLAN.	mld-snooping drop-unknown	By default, dropping unknown IPv6 multicast data is disabled. Unknown IPv6 multicast data is flooded.

Enabling MLD report suppression

This feature enables the device to forward only the first MLD report for an IPv6 multicast group to its directly connected Layer 3 device. Other reports for the same group in the same query interval are discarded. This reduces the multicast traffic.

To enable MLD report suppression:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Enable MLD report suppression.	report-aggregation	By default, MLD report suppression is enabled.

Setting the maximum number of IPv6 multicast groups on a port

You can set the maximum number of IPv6 multicast groups on a port to regulate the port traffic.

Configuration restrictions and guidelines

When you set the maximum number of IPv6 multicast groups on a port, follow these restrictions and guidelines:

· This configuration takes effect only on the IPv6 multicast groups that the port joins dynamically.

· If the number of IPv6 multicast groups on a port exceeds the limit, the system removes all the forwarding entries related to that port. In this case, the receiver hosts attached to that port can join IPv6 multicast groups again before the number of IPv6 multicast groups on the port reaches the limit.

Configuration procedure

To set the maximum number of IPv6 multicast groups on a port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Set the maximum number of IPv6 multicast groups on the port.	mld-snooping group-limit limit [ vlan vlan-list ]	The default setting is 4294967295.

Enabling the IPv6 multicast group replacement feature

This feature enables the device to replace an existing group with a newly joined group when the number of groups exceeds the upper limit. This feature is typically used in the channel switching application. Without this feature, the Layer 2 device discards MLD reports for new groups, and the user cannot change to the new channel.

Configuration restrictions and guidelines

When you enable the IPv6 multicast group replacement feature, follow these restrictions and guidelines:

· This configuration takes effect only on the multicast groups that the port joins dynamically.

· You can enable this feature globally for all ports in MLD-snooping view or for a port in interface view. For a port, the port-specific configuration takes priority over the global configuration.

Configuration procedure

To enable the IPv6 multicast group replacement feature globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter MLD-snooping view.	mld-snooping	N/A
3. Enable the IPv6 multicast group replacement feature globally.	overflow-replace [ vlan vlan-list ]	By default, the IPv6 multicast group replacement feature is disabled.

To enable the IPv6 multicast group replacement on a port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view.	interface interface-type interface-number	N/A
3. Enable the IPv6 multicast group replacement feature on the port.	mld-snooping overflow-replace [ vlan vlan-list ]	By default, the IPv6 multicast group replacement feature is disabled.

Displaying and maintaining MLD snooping

Execute display commands in any view and reset commands in user view.

Task	Command
Display information about Layer 2 IPv6 multicast groups.	display ipv6 l2-multicast ip [ group ipv6-group-address \| source ipv6-source-address ] * [ vlan vlan-id ] [ slot slot-number ]
Display Layer 2 IPv6 multicast group entries.	display ipv6 l2-multicast ip forwarding [ group ipv6-group-address \| source ipv6-source-address ] * [ vlan vlan-id ] [ slot slot-number ]
Display information about Layer 2 IPv6 MAC multicast groups.	display ipv6 l2-multicast mac [ mac-address ] [ vlan vlan-id ] [ slot slot-number ]
Display Layer 2 IPv6 MAC multicast group entries.	display ipv6 l2-multicast mac forwarding [ mac-address ] [ vlan vlan-id ] [ slot slot-number ]
Display MLD snooping status.	display mld-snooping [ global \| vlan vlan-id ]
Display dynamic MLD snooping group entries.	display mld-snooping group [ ipv6-group-address \| ipv6-source-address ] * [ vlan vlan-id ] [ verbose ] [ slot slot-number ]
Display dynamic router port information.	display mld-snooping router-port [ vlan vlan-id ] [ slot slot-number ]
Display static MLD snooping group entries.	display mld-snooping static-group [ ipv6-group-address \| ipv6-source-address ] * [ vlan vlan-id ] [ verbose ] [ slot slot-number ]
Display static router port information.	display mld-snooping static-router-port [ vlan vlan-id ] [ slot slot-number ]
Display statistics for MLD message learned through MLD snooping.	display mld-snooping statistics
Clear dynamic MLD snooping group entries.	reset mld-snooping group { ipv6-group-address [ ipv6-source-address ] \| all } [ vlan vlan-id ]
Clear dynamic router port information.	reset mld-snooping router-port { all \| vlan vlan-id }
Clear statistics for MLD messages learned through MLD snooping.	reset mld-snooping statistics

MLD snooping configuration example

Network requirements

As shown in Figure 15:

· The source sends IPv6 multicast traffic to IPv6 multicast group FF1E::1.

· The client is a receiver host of the IPv6 multicast group.

· The route between the source and the client is reachable.

Configure the AC so that the client can receive the IPv6 multicast traffic from the source.

Figure 15 Network diagram

Configuration procedure

Configuring Router A

# Enable IPv6 multicast routing globally, and enable IPv6 PIM-DM and MLD on the port that connects to the AC. (Details not shown.)

Configuring the AC

1. Configure WLAN services:

# Create VLAN 100.

<AC> system-view

[AC] vlan 100

[AC-vlan100] quit

# Create service template 1, and set the SSID to Multicast for the service template.

[AC] wlan service-template 1

[AC-wlan-st-1] ssid Multicast

# Bind VLAN 100 to service template 1, and enable the service template.

[AC-wlan-st-1] vlan 100

[AC-wlan-st-1] service-template enable

[AC-wlan-st-1] quit

# Create an AP named ap with model WA536-WW, and set the serial ID of the AP to 219801A1NQB117012935.

[AC ]wlan ap ap model WA536-WW

[AC-wlan-ap-ap] serial-id 219801A1NQB117012935

# Bind service template 1 to radio 1, and enable radio 1 for AP ap.

[AC-wlan-ap-ap] radio 1

[AC-wlan-ap-ap-radio-1] service-template 1

[AC-wlan-ap-ap-radio-1] radio enable

[AC-wlan-ap-ap-radio-1] quit

[AC-wlan-ap-ap]quit

2. Configure MLD snooping:

# Enable MLD snooping globally.

[AC] mld-snooping

[AC-mld-snooping] quit

# Enable MLD snooping for VLAN 100.

[AC] vlan 100

[AC-vlan100] mld-snooping enable

[AC-vlan100] quit

3. Configure Ethernet interfaces:

# Configure GigabitEthernet 1/0/2 on the access controller as a trunk port, and assign the port to VLAN 100.

[AC] interface GigabitEthernet 1/0/2

[AC-GigabitEthernet1/0/2] port link-type trunk

[AC-GigabitEthernet1/0/2] port trunk permit vlan 100

[AC-GigabitEthernet1/0/2] quit

Configuring the client

# Configure the client to access the WLAN service with the SSID Multicast and request multicast traffic for IPv6 multicast group FF1E::1. (Details not shown.)

Verifying the configuration

# Display detailed information about dynamic MLD snooping group entries for VLAN 100 on the AC.

[AC] display mld-snooping group vlan 100 verbose

Total 1 entries.

VLAN 100: Total 1 entries.

(::,FF1E::101)

Attribute: local port

FSM information: normal

Host slots (0 in total):

Host ports (1 in total):

WLAN-BSS1/0/20 (00:03:23)

The output shows that WLAN-BSS 1/0/20 on the AC has joined the IPv6 multicast group FF1E::1.

Troubleshooting MLD snooping

Layer 2 multicast forwarding cannot function

Symptom

Layer 2 multicast forwarding cannot function through MLD snooping.

Solution

To resolve the problem:

1. Use the display mld-snooping command to display MLD snooping status.

2. If MLD snooping is not enabled, use the mld-snooping command in system view to enable MLD snooping globally. Then, use the mld-snooping enable command in VLAN view to enable MLD snooping for the VLAN.

3. If MLD snooping is enabled globally but not enabled for the VLAN, use the mld-snooping enable command in VLAN view to enable MLD snooping for the VLAN.

4. If the problem persists, contact H3C Support.

IPv6 multicast group policy does not work

Symptom

Hosts can receive multicast data from IPv6 multicast groups that are not permitted by the IPv6 multicast group policy.

Solution

To resolve the problem:

1. Use the display acl ipv6 command to verify that the configured IPv6 ACL meets the IPv6 multicast group policy requirements.

2. Use the display this command in MLD-snooping view or in a corresponding interface view to verify that the correct IPv6 multicast group policy has been correctly applied. If the applied IPv6 multicast group policy is not correct, use the group-policy or mld-snooping group-policy command to apply the correct IPv6 multicast group policy.

3. Use the display mld-snooping command to verify that dropping unknown IPv6 multicast data is enabled. If dropping unknown IPv6 multicast data is not enabled, use the drop-unknown or mld-snooping drop-unknown command to enable dropping unknown IPv6 multicast data.

4. If the problem persists, contact H3C Support.

Index

Numerics

802

IGMP snooping message 802.1p priority, 24

MLD snooping 802.1p message priority, 45

ACL

IGMP snooping policy, 24

MLD snooping policy, 45

address

IP multicast, 5

MLD snooping message source IPv6 address, 43

aging

IGMP snooping dynamic port aging timer, 18

MLD snooping dynamic port aging timers, 39

application

IP multicast data distribution, 4

architecture

IP multicast network, 5

ASM

IP multicast model), 4

broadcast

IP multicast transmission technique, 2

command and hardware compatibility

IGMP snooping, 14

MLD snooping, 35

configuring

IGMP general query/response parameters, 22

IGMP general query/response parameters (VLAN), 22

IGMP snooping, 11, 14, 28

IGMP snooping basic features, 15

IGMP snooping fast-leave processing, 20

IGMP snooping general query/response parameters (global), 22

IGMP snooping message parameters, 22

IGMP snooping message source IP address, 23

IGMP snooping multicast group policy, 24

IGMP snooping multicast groups on port, 26

IGMP snooping policy, 24

IGMP snooping port feature, 18

IGMP snooping querier, 21

IGMP snooping simulated member host, 19

IGMP snooping static port, 19

MLD general query/response parameters, 42

MLD general query/response parameters (global), 43

MLD general query/response parameters (VLAN), 43

MLD querier, 42

MLD snooping, 32, 35, 49

MLD snooping basic features, 36

MLD snooping IPv6 multicast group policy, 45

MLD snooping message parameters, 43

MLD snooping message source IPv6 address, 43

MLD snooping policy, 45

MLD snooping port features, 39

MLD snooping report suppression, 47

MLD snooping simulated member host port, 40

MLD snooping static ports, 40

disabling

IGMP snooping dynamic router port change, 20

MLD snooping dynamic router port change, 41

displaying

IGMP snooping, 27

MLD snooping, 48

done message (MLD snooping), 34

dropping

IGMP snooping unknown multicast data, 25

MLD snooping unknown IPv6 multicast data, 46

dynamic

IGMP snooping dynamic member port, 12

IGMP snooping dynamic port aging timer, 18

IGMP snooping dynamic router port, 12

IGMP snooping dynamic router port change, 20

MLD snooping dynamic member port, 33

MLD snooping dynamic port aging timers, 39

MLD snooping dynamic router port, 33

MLD snooping dynamic router port change, 41

enabling

IGMP snooping multicast group replacement, 27

IGMP snooping multicast group replacement (global), 27

IGMP snooping multicast group replacement (on port), 27

IGMP snooping querier, 21

IGMP snooping report suppression, 26

IGMP snooping unknown multicast data drop, 25

IGMP snooping unknown multicast data drop (global), 25

IGMP snooping unknown multicast data drop (VLAN), 25

MLD snooping, 36

MLD snooping (MLD snooping view), 36

MLD snooping (VLAN view), 36

MLD snooping fast-leave processing, 41

MLD snooping fast-leave processing (global), 41

MLD snooping fast-leave processing (on port), 41

MLD snooping IPv6 multicast group replacement, 48

MLD snooping IPv6 multicast group replacement (global), 48

MLD snooping IPv6 multicast group replacement (on port), 48

MLD snooping IPv6 multicast unknown data drop, 46

MLD snooping IPv6 multicast unknown data drop (global), 46

MLD snooping IPv6 multicast unknown data drop (VLAN), 46

MLD snooping querier, 42

Ethernet

IP multicast MAC address, 8

IP multicast overview, 1

fast-leave processing

IGMP snooping, 20

MLD snooping, 41

filtering

IGMP snooping unknown multicast data drop, 25

MLD snooping IPv6 multicast unknown data drop, 46

MLD snooping policy, 45

forwarding

IGMP snooping forwarding entries, 17

IGMP snooping last member query interval, 17

MLD snooping entries max, 38

MLD snooping last member query interval, 38

troubleshooting MLD snooping Layer 2 forwarding, 51

group

IGMP snooping multicast group policy, 24

IGMP snooping multicast group replacement, 27

MLD snooping IPv6 multicast group policy, 45

MLD snooping IPv6 multicast group replacement, 48

MLD snooping IPv6 multicast groups on port, 47

host

IGMP snooping simulated member host, 19

MLD snooping simulated member host port, 40

IGMP

snooping. See IGMP snooping

IGMP snooping

basic configuration, 15

command and hardware compatibility, 14

configuration, 11, 14, 28

display, 27

dynamic port aging timer, 18

dynamic router port change disable, 20

enable, 15

fast-leave processing enable, 20

forwarding entries, 17

general query, 13

general query/response parameter configuration, 22

how it works, 13

IGMP last member query interval configuration restrictions, 17

last member query interval, 17

leave message, 13

maintain, 27

membership report, 13

message 802.1p priority, 24

message parameter configuration, 22

message source IP address, 23

multicast group policy configuration, 24

multicast group replacement, 27

multicast groups on port, 26

policy configuration, 24

port, 11

port feature configuration, 18

protocols and standards, 14

querier configuration, 21

querier enable, 21

report suppression, 26

simulated member host configuration, 19

static port configuration, 19

troubleshoot, 30

troubleshoot Layer 2 multicast forwarding, 30

troubleshoot multicast group filter, 31

unknown multicast data drop, 25

version specification, 16

IGMPv1 snooping version specification, 16

IGMPv2 snooping version specification, 16

IGMPv3 snooping version specification, 16

interval

IGMP snooping last member query interval, 17

IP addressing

IGMP snooping message source IP address, 23

IP multicast address, 5

IP multicast

address, 5

architecture, 5

ASM model, 4

broadcast transmission technique, 2

common notation, 4

data distribution, 4

Ethernet multicast MAC address, 8

features, 3

IGMP general query/response parameters, 22

IGMP snooping basic configuration, 15

IGMP snooping configuration, 11, 14, 28

IGMP snooping display, 27

IGMP snooping dynamic router port change, 20

IGMP snooping fast-leave processing, 20

IGMP snooping forwarding entries, 17

IGMP snooping general query, 13

IGMP snooping group policy, 24

IGMP snooping groups on port, 26

IGMP snooping last member query interval, 17

IGMP snooping leave message, 13

IGMP snooping maintain, 27

IGMP snooping membership report, 13

IGMP snooping message 802.1p priority, 24

IGMP snooping message parameters, 22

IGMP snooping message source IP address, 23

IGMP snooping multicast group replacement, 27

IGMP snooping policy, 24

IGMP snooping port, 11

IGMP snooping port feature, 18

IGMP snooping protocols and standards, 14

IGMP snooping querier, 21

IGMP snooping report suppression, 26

IGMP snooping static port, 19

IGMP snooping unknown multicast data drop, 25

IGMP snooping version specification, 16

Layer 2 protocols, 10

Layer 3 protocols, 9

MLD snooping 802.1p message priority, 45

MLD snooping basic configuration, 36

MLD snooping configuration, 32, 35, 49

MLD snooping display, 48

MLD snooping dynamic port aging timers, 39

MLD snooping dynamic router port change, 41

MLD snooping fast-leave processing enable, 41

MLD snooping general query/response parameters, 42

MLD snooping group policy, 45

MLD snooping group replacement, 48

MLD snooping groups on port, 47

MLD snooping last member query interval, 38

MLD snooping maintain, 48

MLD snooping message parameters, 43

MLD snooping message source IPv6 address, 43

MLD snooping policy, 45

MLD snooping port feature configuration, 39

MLD snooping port types, 32

MLD snooping protocols and standards, 35

MLD snooping querier configuration, 42

MLD snooping report suppression, 47

MLD snooping simulated member host port, 40

MLD snooping static port configuration, 40

MLD snooping unknown data drop, 46

models, 4

multicast transmission technique, 2

overview, 1

protocols and standards, 9

SFM model, 5

SSM model, 5

transmission techniques, 1

troubleshooting IGMP snooping, 30

troubleshooting IGMP snooping Layer 2 multicast forwarding, 30

troubleshooting IGMP snooping multicast group filter, 31

troubleshooting MLD snooping, 51

troubleshooting MLD snooping group policy, 51

troubleshooting MLD snooping Layer 2 forwarding, 51

unicast transmission technique, 1

IPv4

Ethernet multicast MAC address, 8

IP multicast address, 5

IPv6

Ethernet multicast MAC address, 8

IP multicast address, 5

MLD snooping dynamic router port change, 41

MLD snooping simulated member host port, 40

Layer 2

IP multicast protocols, 10

troubleshooting IGMP snooping Layer 2 multicast forwarding, 30

troubleshooting MLD snooping Layer 2 forwarding, 51

Layer 3

IP multicast protocols, 9

leave message

IGMP snooping, 13

MAC addressing

Ethernet multicast MAC address, 8

MLD snooping basic configuration, 36

MLD snooping configuration, 32, 35, 49

maintaining

IGMP snooping, 27

MLD snooping, 48

mapping

MLD snooping basic configuration, 36

MLD snooping configuration, 32, 35, 49

member

IGMP snooping router port, 12

IGMP snooping simulated member host, 19

MLD snooping member port, 33

MLD snooping simulated member host port, 40

message

IGMP snooping leave, 13

IGMP snooping message 802.1p priority, 24

IGMP snooping message parameters, 22

MLD snooping 802.1p message priority, 45

MLD snooping basic configuration, 36

MLD snooping configuration, 32, 35, 49

MLD snooping done, 34

MLD snooping fast-leave processing enable, 41

MLD snooping message source IPv6 address, 43

MLD

snooping. See MLD snooping

MLD snooping

802.1p message priority, 45

basic configuration, 36

command and hardware compatibility, 35

configuration, 32, 35, 49

display, 48

done message, 34

dynamic port aging timers, 39

dynamic router port change disable, 41

enable, 36

fast-leave processing enable, 41

forwarding entries max, 38

general query, 34

general query/response parameter configuration, 42

how it works, 34

IPv6 multicast group policy, 45

IPv6 multicast group replacement, 48

IPv6 multicast groups on port, 47

IPv6 multicast unknown data drop, 46

last listener query interval enable restrictions, 38

last member query interval, 38

maintain, 48

membership report, 34

message parameter configuration, 43

message source IPv6 address, 43

policy configuration, 45

port feature configuration, 39

port types, 32

protocols and standards, 35

querier configuration, 42

querier enable, 42

report suppression, 47

simulated member host port, 40

static port configuration, 40

troubleshoot, 51

troubleshoot IPv6 multicast group policy, 51

troubleshoot MLD snooping Layer 2 forwarding, 51

version specification, 37

MLDv1 snooping version specification, 37

MLDv2 snooping version specification, 37

model

IP multicast, 4

IP multicast ASM, 4

IP multicast SFM, 5

IP multicast SSM, 5

multicast

IP multicast transmission technique, 2

network

IGMP snooping basic configuration, 15

IP multicast address, 5

IP multicast architecture, 5

IP multicast models, 4

MLD snooping basic configuration, 36

network management

IGMP snooping configuration, 11, 14, 28

IP multicast overview, 1

MLD snooping configuration, 32, 35, 49

transmission techniques, 1

parameter

IGMP general query/response parameters, 22

IGMP snooping message parameters, 22

policy

IGMP snooping multicast group policy, 24

IGMP snooping policy, 24

MLD snooping IPv6 multicast group policy, 45

MLD snooping policy, 45

port

IGMP snooping basic configuration, 15

IGMP snooping configuration, 11, 14, 28

IGMP snooping dynamic port aging timer, 18

IGMP snooping dynamic router port change, 20

IGMP snooping fast-leave processing, 20

IGMP snooping multicast group replacement, 27

IGMP snooping multicast groups on port, 26

IGMP snooping port, 11

IGMP snooping port feature, 18

IGMP snooping simulated member host, 19

IGMP snooping static port, 19

MLD snooping basic configuration, 36

MLD snooping configuration, 32, 35, 49

MLD snooping dynamic port aging timers, 39

MLD snooping dynamic router port change, 41

MLD snooping fast-leave processing enable, 41

MLD snooping IPv6 multicast group policy, 45

MLD snooping IPv6 multicast group replacement, 48

MLD snooping IPv6 multicast groups on port, 47

MLD snooping IPv6 multicast unknown data drop, 46

MLD snooping policy, 45

MLD snooping port feature configuration, 39

MLD snooping port types, 32

MLD snooping simulated member host port, 40

MLD snooping static port configuration, 40

procedure

configuring IGMP general query/response parameters, 22

configuring IGMP general query/response parameters (VLAN), 22

configuring IGMP snooping, 14

configuring IGMP snooping basic features, 15

configuring IGMP snooping fast-leave processing configuration, 20

configuring IGMP snooping general query/response parameters (global), 22

configuring IGMP snooping message parameters, 22

configuring IGMP snooping message source IP address, 23

configuring IGMP snooping multicast group policy, 24

configuring IGMP snooping multicast groups on port, 26

configuring IGMP snooping policy, 24

configuring IGMP snooping port feature, 18

configuring IGMP snooping querier, 21

configuring IGMP snooping simulated member host, 19

configuring IGMP snooping static port, 19

configuring MLD general query/response parameters, 42

configuring MLD general query/response parameters (global), 43

configuring MLD general query/response parameters (VLAN), 43

configuring MLD snooping, 35

configuring MLD snooping basic features, 36

configuring MLD snooping group policy, 45

configuring MLD snooping message parameters, 43

configuring MLD snooping message source IPv6 address, 43

configuring MLD snooping policy, 45

configuring MLD snooping port features, 39

configuring MLD snooping querier, 42

configuring MLD snooping report suppression, 47

configuring MLD snooping simulated member host port, 40

configuring MLD snooping static ports, 40

disabling IGMP snooping dynamic router port change, 20

disabling MLD snooping dynamic router port change, 41

displaying IGMP snooping, 27

displaying MLD snooping, 48

enabling IGMP snooping, 15

enabling IGMP snooping multicast group replacement, 27

enabling IGMP snooping multicast group replacement (global), 27

enabling IGMP snooping multicast group replacement (on port), 27

enabling IGMP snooping querier, 21

enabling IGMP snooping report suppression, 26

enabling IGMP snooping unknown multicast data drop, 25

enabling IGMP snooping unknown multicast data drop (global), 25

enabling IGMP snooping unknown multicast data drop (VLAN), 25

enabling MLD snooping, 36

enabling MLD snooping (MLD snooping view, 36

enabling MLD snooping (VLAN view), 36

enabling MLD snooping fast-leave processing, 41

enabling MLD snooping fast-leave processing (global), 41

enabling MLD snooping fast-leave processing (on port), 41

enabling MLD snooping IPv6 multicast group replacement, 48

enabling MLD snooping IPv6 multicast group replacement (global), 48

enabling MLD snooping IPv6 multicast group replacement (on port), 48

enabling MLD snooping IPv6 multicast unknown data drop, 46

enabling MLD snooping IPv6 multicast unknown data drop (global), 46

enabling MLD snooping IPv6 multicast unknown data drop (VLAN), 46

enabling MLD snooping querier, 42

maintaining IGMP snooping, 27

maintaining MLD snooping, 48

setting IGMP last member query interval (global), 17

setting IGMP last member query interval (VLAN), 18

setting IGMP snooping dynamic port aging timer, 18

setting IGMP snooping dynamic port aging timer (global), 18

setting IGMP snooping dynamic port aging timer (VLAN), 18

setting IGMP snooping forwarding entries, 17

setting IGMP snooping last member query interval, 17

setting IGMP snooping message 802.1 priority (global), 24

setting IGMP snooping message 802.1p priority, 24

setting IGMP snooping message 802.1p priority (VLAN), 24

setting MLD last listener query interval (global), 38

setting MLD last listener query interval (VLAN), 38

setting MLD snooping 802.1p message priority, 45

setting MLD snooping 802.1p message priority (global), 45

setting MLD snooping 802.1p message priority (VLAN), 45

setting MLD snooping dynamic port aging timers, 39

setting MLD snooping dynamic port aging timers (global), 39

setting MLD snooping dynamic port aging timers (VLAN), 39

setting MLD snooping forwarding entries max, 38

setting MLD snooping IPv6 multicast groups on port, 47

setting MLD snooping last member query interval, 38

specifying IGMP snooping version, 16

specifying MLD snooping version, 37

specifying MLD snooping version (MLD snooping view), 37

specifying MLD snooping version (VLAN view), 37

troubleshooting IGMP snooping Layer 2 forwarding, 30

troubleshooting IGMP snooping multicast group filter, 31

troubleshooting MLD snooping group policy, 51

troubleshooting MLD snooping Layer 2 forwarding, 51

protocols and standards

IGMP snooping, 14

IP multicast, 9

Layer 2 multicast, 10

Layer 3 multicast, 9

MLD snooping, 35

querier

IGMP snooping querier, 21, 21

MLD snooping querier configuration, 42

MLD snooping querier enable, 42

querying

IGMP snooping general query, 13

IGMP snooping general query/response parameters, 22

IGMP snooping querier, 21, 21

MLD general query/response parameters, 42

MLD snooping general query, 34

MLD snooping message parameters, 43

MLD snooping querier configuration, 42

MLD snooping querier enable, 42

rendezvous point tree. Use RPT

reporting

IGMP snooping membership, 13

IGMP snooping report suppression, 26

MLD snooping membership report, 34

MLD snooping report suppression, 47

restrictions

IGMP last member query interval configuration, 17

MLD snooping last listener query interval enable, 38

router

IGMP snooping router port, 12

MLD snooping router port, 33

routing

IGMP general query/response parameters, 22

IGMP snooping basic configuration, 15

IGMP snooping configuration, 11, 14, 28

IGMP snooping dynamic router port change, 20

IGMP snooping forwarding entries, 17

IGMP snooping last member query interval, 17

IGMP snooping message 802.1p priority, 24

IGMP snooping message parameters, 22

IGMP snooping message source IP address, 23

IGMP snooping multicast group policy, 24

IGMP snooping policy, 24

IGMP snooping port feature, 18

IGMP snooping simulated member host, 19

IGMP snooping static port, 19

IGMP snooping version specification, 16

IP multicast address, 5

IP multicast overview, 1

IP multicast transmission techniques, 1

MLD general query/response parameters, 42

MLD snooping 802.1p message priority, 45

MLD snooping basic configuration, 36

MLD snooping configuration, 32, 35, 49

MLD snooping dynamic router port change, 41

MLD snooping forwarding entries max, 38

MLD snooping last member query interval, 38

MLD snooping message parameters, 43

MLD snooping message source IPv6 address, 43

MLD snooping port feature configuration, 39

MLD snooping simulated member host port, 40

RPT

IP multicast notation, 4

setting

IGMP last member query interval, 17

IGMP last member query interval (global), 17

IGMP last member query interval (VLAN), 18

IGMP snooping dynamic port aging timer, 18

IGMP snooping dynamic port aging timer (global), 18

IGMP snooping dynamic port aging timer (VLAN), 18

IGMP snooping forwarding entries, 17

IGMP snooping message 802.1p priority, 24

IGMP snooping message 802.1p priority (global), 24

IGMP snooping message 802.1p priority (VLAN), 24

MLD last listener query interval, 38

MLD last listener query interval (global), 38

MLD last listener query interval (VLAN), 38

MLD snooping 802.1p message priority, 45

MLD snooping 802.1p message priority (global), 45

MLD snooping 802.1p message priority (VLAN), 45

MLD snooping dynamic port aging timers, 39

MLD snooping dynamic port aging timers (global), 39

MLD snooping dynamic port aging timers (VLAN), 39

MLD snooping forwarding entries max, 38

MLD snooping IPv6 multicast groups on port, 47

SFM

IP multicast model, 5

shortest path tree. Use SPT

simulated member host, 19

snooping

IGMP snooping configuration, 11

MLD snooping, 32

MLD snooping configuration, 35

specifying

IGMP snooping version, 16

MLD snooping version, 37

MLD snooping version (MLD snooping view), 37

MLD snooping version (VLAN view), 37

SPT

IP multicast notation, 4

SSM

IP multicast model, 5

static

IGMP snooping static member port, 12

IGMP snooping static port, 19

IGMP snooping static router port, 12

MLD snooping static member port, 33

MLD snooping static port configuration, 40

MLD snooping static router port, 33

suppressing

IGMP snooping report suppression, 26

MLD snooping report suppression, 47

switching

IP multicast overview, 1

IP multicast transmission techniques, 1

timer

IGMP snooping dynamic member port aging timer, 12

IGMP snooping dynamic port aging timer, 18

IGMP snooping dynamic router port aging timer, 12

MLD snooping dynamic port aging timers, 39

transmitting

IP multicast, 2

IP multicast broadcast, 2

IP multicast overview, 1

IP multicast transmission techniques, 1

IP multicast unicast, 1

troubleshooting

IGMP snooping, 30

IGMP snooping Layer 2 multicast forwarding, 30

IGMP snooping multicast group filter, 31

MLD snooping, 51

MLD snooping IPv6 multicast group policy, 51

MLD snooping Layer 2 forwarding, 51

unicast

IP multicast transmission technique, 1

version

IGMP snooping specification, 16

IGMPv1 snooping, 16

IGMPv2 snooping, 16

IGMPv3 snooping, 16

MLD snooping, 37

VLAN

IGMP general query/response parameters, 22

IGMP snooping basic configuration, 15

IGMP snooping configuration, 11, 14, 28

IGMP snooping dynamic port aging timer, 18, 18

IGMP snooping enable, 15

IGMP snooping fast-leave processing, 20

IGMP snooping message 802.1p priority, 24

IGMP snooping message parameters, 22

IGMP snooping message source IP address, 23

IGMP snooping multicast group replacement, 27

IGMP snooping multicast groups on port, 26

IGMP snooping policy, 24, 24

IGMP snooping port feature, 18

IGMP snooping querier, 21

IGMP snooping querier enable, 21

IGMP snooping simulated member host, 19

IGMP snooping static port, 19

IGMP snooping unknown multicast data drop, 25

IGMP snooping version specification, 16

MLD general query/response parameter configuration (VLAN), 43

MLD general query/response parameters, 42

MLD snooping 802.1p message priority, 45

MLD snooping basic configuration, 36

MLD snooping configuration, 49

MLD snooping dynamic port aging timers, 39

MLD snooping dynamic port aging timers setting, 39

MLD snooping enable, 36

MLD snooping fast-leave processing enable, 41

MLD snooping message parameters, 43

MLD snooping message source IPv6 address, 43

MLD snooping policy, 45, 45

MLD snooping port feature configuration, 39

MLD snooping querier enable, 42

MLD snooping static port configuration, 40

MLD snooping version, 37

08-IP Multicast

Unicast

Multicast

Common notations in multicast

Multicast benefits

Multicast applications

ASM model

SFM model

SSM model

Ethernet multicast MAC addresses

Multicast protocols

Layer 3 multicast protocols

Layer 2 multicast protocols

Overview

Router ports

Member ports

General query

IGMP report

Leave message

Protocols and standards

Enabling IGMP snooping

Specifying an IGMP snooping version

Configuration restrictions and guidelines

Setting the IGMP last member query interval globally

Setting the IGMP last member query interval in a VLAN

Setting aging timers for dynamic ports

Setting the aging timers for dynamic ports globally

Setting the aging timers for dynamic ports in a VLAN

Configuring a port as a simulated member host

Configuration restrictions and guidelines

Configuration procedure

Disabling a port from becoming a dynamic router port

Configuring the IGMP snooping querier

Enabling the IGMP snooping querier

Configuring parameters for IGMP general queries and responses globally

Configuring source IP addresses for IGMP messages

Setting the 802.1p priority for IGMP messages globally

Setting the 802.1p priority for IGMP messages in a VLAN

Configuring IGMP snooping policies

Configuring a multicast group policy

Configuration restrictions and guidelines

Configuration procedure

Enabling dropping unknown multicast data

Configuration restrictions and guidelines

Configuration procedure

Enabling IGMP report suppression

Configuration restrictions and guidelines

Configuration procedure

Enabling the multicast group replacement feature

Configuration restrictions and guidelines

Configuration procedure

Displaying and maintaining IGMP snooping

IGMP snooping configuration example

Configuring Router A

Configuring the AC

Configuring the client

Troubleshooting IGMP snooping

Layer 2 multicast forwarding cannot function

Symptom

Solution

Symptom

Solution

Overview

Router ports

Member ports

General query

MLD report

Done message

Protocols and standards

MLD snooping configuration task list

Setting the MLD last listener query interval

Configuration restrictions and guidelines

Setting the MLD last listener query interval globally

Setting the MLD last listener query interval in a VLAN

Setting the aging timers for dynamic ports globally

Setting the aging timers for dynamic ports in a VLAN

Enabling fast-leave processing

Configuration restrictions and guidelines

Configuration procedure

Configuring parameters for MLD general queries and responses globally