Contents

Configuring IGMP snooping· 1

Overview· 1

IGMP snooping ports· 1

How IGMP snooping works· 3

Protocols and standards· 4

General configuration restrictions and guidelines· 4

IGMP snooping configuration task list 5

Configuring basic IGMP snooping features· 5

Enabling IGMP snooping· 5

Specifying an IGMP snooping version· 6

Setting the maximum number of IGMP snooping forwarding entries· 7

Setting the IGMP last member query interval 7

Configuring IGMP snooping port features· 8

Setting aging timers for dynamic ports· 8

Configuring static ports· 9

Configuring a port as a simulated member host 10

Enabling fast-leave processing· 10

Disabling a port from becoming a dynamic router port 11

Configuring the IGMP snooping querier 11

Configuration prerequisites· 11

Enabling the IGMP snooping querier 12

Configuring parameters for IGMP general queries and responses· 12

Configuring parameters for IGMP messages· 13

Configuration prerequisites· 13

Configuring source IP addresses for IGMP messages· 13

Setting the 802.1p priority for IGMP messages· 14

Configuring IGMP snooping policies· 15

Configuring a multicast group policy· 15

Enabling multicast source port filtering· 16

Enabling dropping unknown multicast data· 16

Enabling IGMP report suppression· 17

Setting the maximum number of multicast groups on a port 17

Enabling multicast group replacement 18

Displaying and maintaining IGMP snooping· 18

IGMP snooping configuration examples· 20

Group policy and simulated joining configuration example· 20

Static port configuration example· 22

IGMP snooping querier configuration example· 24

Troubleshooting IGMP snooping· 27

Layer 2 multicast forwarding cannot function· 27

Multicast group policy does not work· 27

 

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 1, when IGMP snooping is not enabled, the Layer 2 switch floods multicast packets to all hosts in a VLAN. When IGMP snooping is enabled, the Layer 2 switch forwards multicast packets of known multicast groups to only the receivers.

Figure 1 Multicast packet transmission without and with IGMP snooping

IGMP snooping ports

As shown in Figure 2, IGMP snooping runs on Switch A and Switch 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 2 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 2, GigabitEthernet 1/0/1 of Switch A and GigabitEthernet 1/0/1 of Switch 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 or receives a PIM hello message, 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 either of the messages before the timer expires, the timer is reset. If the port does not receive either of the messages 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 2, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 of Switch A and GigabitEthernet 1/0/2 of Switch 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. If the report does not pass ACL filtering, the Layer 2 device drops this report. 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. For more information about the mechanism, see "Configuring IGMP."

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

General configuration restrictions and guidelines

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

·     For a VLAN configured with IGMP snooping, if you change the VPN instance bound to the VLAN interface, Layer 2 multicast traffic for the VLAN is interrupted. In this case, you must execute the reset igmp-snooping group command so that new IGMP snooping forwarding entries can be created.

·     For IGMP reports received from secondary VLANs, the relevant IGMP snooping forwarding entries are maintained by the primary VLAN. Therefore, you need to configure IGMP snooping only for the primary VLAN. The IGMP snooping configuration made for secondary VLANs does not take effect. For more information about primary VLANs and secondary VLANs, see Layer 2—LAN Switching Configuration Guide.

·     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.

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

 

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 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.

Enabling 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.

 

Enabling 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 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 switch 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.

Specifying an IGMP snooping version 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	N/A
3.     Specify an IGMP snooping version for the specified VLANs.	version version-number vlan vlan-list	The default setting is 2.

 

Specifying 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 set the maximum number of IGMP snooping forwarding entries, including dynamic entries and static entries. When the number of forwarding entries on the switch reaches the upper limit, the switch does not automatically remove any existing entries. As a best practice, manually remove some entries to allow new entries to be created.

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 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.

·     If a dynamic router port receives a PIMv2 hello message, the aging timer for the port is specified by the hello message. In this case, the router-aging-time or igmp-snooping router-aging-time command does not take effect on the port.

·     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 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 switch 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-leaving 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.

Enabling 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.

 

Enabling 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 an IGMP general query or PIM hello message for testing purposes. In this case, the following problems might exist:

·     The port that receives the IGMP general query or PIM hello message becomes a dynamic router port. Before its aging timer expires, this dynamic router port receives all multicast packets within the VLAN where the port belongs and forwards them to the host. The receiver host will receive multicast data that it does not want to receive.

·     The IGMP general query or PIM hello message that the host sends affects the multicast routing protocol state on Layer 3 devices, such as the IGMP querier or DR election. This might further cause network interruption.

To solve these problems and to improve network security and the control over multicast users, you can disable a port from becoming a dynamic router port.

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 switch 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 multicast 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 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 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 deleting 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 for a VLAN 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.

Configuration restrictions and guidelines

When you configure parameters for IGMP general queries and responses, follow these restrictions and guidelines:

·     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 configure 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 the 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.

 

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.

To configure source IP addresses 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.     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 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 switch, it forwards IGMP messages in their 802.1p priority order, from highest to lowest. You can assign higher 802.1p priority to IGMP messages that are created or forwarded by the switch.

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. The global configuration takes effect on all VLANs.

 

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 to be 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 switch to filter IGMP reports based on the used ACL that specifies the multicast groups and the optional sources. Use this feature to control the multicast groups that receiver hosts can join.

Configuration restrictions and guidelines

When you configure a multicast group policy, follow these 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.

Configuring 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.

 

Configuring 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 multicast source port filtering

This feature enables the switch to discard all multicast data packets and to accept multicast protocol packets. You can enable this feature on ports that connect only to multicast receivers.

You can enable this feature for the specified ports in IGMP-snooping view or for a port in interface view. For a port, the configuration in interface view has the same priority as the configuration in IGMP-snooping view, and the most recent configuration takes effect.

Enabling multicast source port filtering for the specified ports

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enter IGMP-snooping view.	igmp-snooping	N/A
3.     Enable multicast source port filtering.	source-deny port interface-list	By default, multicast source port filtering is disabled.

 

Enabling multicast source port filtering for a port

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enter Layer 2 Ethernet interface view.	interface interface-type interface-number	N/A
3.     Enable multicast source port filtering.	igmp-snooping source-deny	By default, multicast source port filtering is disabled.

 

Enabling dropping unknown multicast data

This feature enables the switch 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.

Configuration restrictions and guidelines

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

·     To avoid multicast forwarding exceptions, do not globally enable this feature when the switch joins an IRF 3 system. For more informational about IRF 3, see Virtualization Technologies Configuration Guide.

·     You can enable this feature 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 switch.

·     If you enable dropping unknown IPv6 and IPv4 multicast data, enable both of them globally or for the same VLANs to ensure correct multicast forwarding. For more information about enabling dropping unknown IPv6 multicast data, see "Configuring MLD snooping."

·     When dropping unknown multicast data is enabled, the switch still forwards unknown multicast data to other router ports in the VLAN.

Enabling 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 in the VLAN to which the data belongs.

 

Enabling dropping unknown multicast data in 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 in the VLAN to which the data belongs.

 

Enabling IGMP report suppression

This feature enables the switch 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 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 multicast group replacement

This feature enables the switch 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 switch discards IGMP reports for new groups, and the user cannot change to the new channel.

Configuration restrictions and guidelines

When you enable multicast group replacement, follow these 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.

Enabling multicast group replacement globally

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

 

Enabling 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 multicast group replacement on a port.	igmp-snooping overflow-replace [ vlan vlan-list ]	By default, multicast group replacement 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 forwarding entries (in standalone mode).	display igmp-snooping group [ group-address | source-address ] * [ vlan vlan-id ] [ verbose ] [ slot slot-number ]
Display dynamic IGMP snooping forwarding entries (in IRF mode).	display igmp-snooping group [ group-address | source-address ] * [ vlan vlan-id ] [ verbose ] [ chassis chassis-number slot slot-number ]
Display dynamic router port information (in standalone mode).	display igmp-snooping router-port [ vlan vlan-id ] [ slot slot-number ]
Display dynamic router port information (in IRF mode).	display igmp-snooping router-port [ vlan vlan-id ] [ chassis chassis-number slot slot-number ]
Display static IGMP snooping forwarding entries (in standalone mode).	display igmp-snooping static-group [ group-address | source-address ] * [ vlan vlan-id ] [ verbose ] [ slot slot-number ]
Display static IGMP snooping forwarding entries (in IRF mode).	display igmp-snooping static-group [ group-address | source-address ] * [ vlan vlan-id ] [ verbose ] [ chassis chassis-number slot slot-number ]
Display static router port information (in standalone mode).	display igmp-snooping static-router-port [ vlan vlan-id ] [ slot slot-number ]
Display static router port information (in IRF mode).	display igmp-snooping static-router-port [ vlan vlan-id ] [ chassis chassis-number 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 (in standalone mode).	display l2-multicast ip [ group group-address | source source-address ] * [ vlan vlan-id ] [ slot slot-number ]
Display information about Layer 2 IP multicast groups (in IRF mode).	display l2-multicast ip [ group group-address | source source-address ] * [ vlan vlan-id ] [ chassis chassis-number slot slot-number ]
Display Layer 2 IP multicast group entries (in standalone mode).	display l2-multicast ip forwarding [ group group-address | source source-address ] * [ vlan vlan-id ] [ slot slot-number ]
Display Layer 2 IP multicast group entries (in IRF mode).	display l2-multicast ip forwarding [ group group-address | source source-address ] * [ vlan vlan-id ] [ chassis chassis-number slot slot-number ]
Display information about Layer 2 MAC multicast groups (in standalone mode).	display l2-multicast mac [ mac-address ] [ vlan vlan-id ] [ slot slot-number ]
Display information about Layer 2 MAC multicast groups (in IRF mode).	display l2-multicast mac [ mac-address ] [ vlan vlan-id ] [ chassis chassis-number slot slot-number ]
Display Layer 2 MAC multicast group entries (in standalone mode).	display l2-multicast mac forwarding [ mac-address ] [ vlan vlan-id ] [ slot slot-number ]
Display Layer 2 MAC multicast group entries (in IRF mode).	display l2-multicast mac forwarding [ mac-address ] [ vlan vlan-id ] [ chassis chassis-number slot slot-number ]
Clear dynamic IGMP snooping forwarding 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 the IGMP messages learned through IGMP snooping.	reset igmp-snooping statistics

 

IGMP snooping configuration examples

Group policy and simulated joining configuration example

Network requirements

As shown in Figure 3, Router A runs IGMPv2 and acts as the IGMP querier. Switch A runs IGMPv2 snooping.

Configure a group policy and simulated joining to meet the following requirements:

·     Host A and Host B receive only the multicast data addressed to multicast group 224.1.1.1. Multicast data can be forwarded through GigabitEthernet 1/0/3 and GigabitEthernet 1/0/4 of Switch A uninterruptedly, even though Host A and Host B fail to receive the multicast data.

·     Switch A will drop unknown multicast data instead of flooding it in VLAN 100.

Figure 3 Network diagram

 

Configuration procedure

1.     Assign an IP address and subnet mask to each interface according to Figure 3. (Details not shown.)

2.     Configure Router A:

# Enable IP multicast routing.

<RouterA> system-view

[RouterA] multicast routing

[RouterA-mrib] quit

# Enable IGMP on GigabitEthernet 1/0/1.

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] igmp enable

[RouterA-GigabitEthernet1/0/1] quit

# Enable PIM-DM on GigabitEthernet 1/0/2.

[RouterA] interface gigabitethernet 1/0/2

[RouterA-GigabitEthernet1/0/2] pim dm

[RouterA-GigabitEthernet1/0/2] quit

3.     Configure Switch A:

# Enable IGMP snooping globally.

<SwitchA> system-view

[SwitchA] igmp-snooping

[SwitchA-igmp-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/4 to the VLAN.

[SwitchA] vlan 100

[SwitchA-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/4

# Enable IGMP snooping, and enable dropping unknown multicast data for VLAN 100.

[SwitchA-vlan100] igmp-snooping enable

[SwitchA-vlan100] igmp-snooping drop-unknown

[SwitchA-vlan100] quit

# Configure a multicast group policy so that the hosts in VLAN 100 can join only multicast group 224.1.1.1.

[SwitchA] acl number 2001

[SwitchA-acl-basic-2001] rule permit source 224.1.1.1 0

[SwitchA-acl-basic-2001] quit

[SwitchA] igmp-snooping

[SwitchA-igmp-snooping] group-policy 2001 vlan 100

[SwitchA-igmp-snooping] quit

# Configure GigabitEthernet 1/0/3 and GigabitEthernet 1/0/4 as simulated member hosts of multicast group 224.1.1.1.

[SwitchA] interface gigabitethernet 1/0/3

[SwitchA-GigabitEthernet1/0/3] igmp-snooping host-join 224.1.1.1 vlan 100

[SwitchA-GigabitEthernet1/0/3] quit

[SwitchA] interface gigabitethernet 1/0/4

[SwitchA-GigabitEthernet1/0/4] igmp-snooping host-join 224.1.1.1 vlan 100

[SwitchA-GigabitEthernet1/0/4] quit

Verifying the configuration

# Send IGMP reports from Host A and Host B to join multicast groups 224.1.1.1 and 224.2.2.2. (Details not shown.)

# Display dynamic IGMP snooping forwarding entries for VLAN 100 on Switch A.

[SwitchA] display igmp-snooping group vlan 100

Total 1 entries.

 

VLAN 100: Total 1 entries.

  (0.0.0.0, 224.1.1.1)

    Host slots (0 in total):

    Host ports (2 in total):

      GE1/0/3                              (00:03:23)

      GE1/0/4                              (00:04:10)

The output shows the following information:

·     Host A and Host B have joined multicast group 224.1.1.1 through the member ports GigabitEthernet 1/0/3 and GigabitEthernet1/0/4 on Switch A, respectively.

·     Host A and Host B have failed to join multicast group 224.2.2.2.

Static port configuration example

Network requirements

As shown in Figure 4:

·     Router A runs IGMPv2 and acts as the IGMP querier. Switch A, Switch B, and Switch C run IGMPv2 snooping.

·     Host A and host C are permanent receivers of multicast group 224.1.1.1.

Configure static ports to meet the following requirements:

·     To enhance the reliability of multicast traffic transmission, configure GigabitEthernet 1/0/3 and GigabitEthernet 1/0/5 on Switch C as static member ports for multicast group 224.1.1.1.

·     Suppose the STP runs on the network. To avoid data loops, the forwarding path from Switch A to Switch C is blocked. Multicast data flows to the receivers attached to Switch C only along the path of Switch A—Switch B—Switch C. When this path is blocked, at least one IGMP query-response cycle must be completed before multicast data flows to the receivers along the path of Switch A—Switch C. In this case, the multicast delivery is interrupted during the process. For more information about the STP, see Layer 2—LAN Switching Configuration Guide.

Configure GigabitEthernet 1/0/3 on Switch A as a static router port. Then, multicast data can flow to the receivers nearly uninterruptedly along the path of Switch A—Switch C when the path of Switch A—Switch B—Switch C is blocked.

Figure 4 Network diagram

 

Configuration procedure

1.     Assign an IP address and subnet mask to each interface according to Figure 4. (Details not shown.)

2.     Configure Router A:

# Enable IP multicast routing.

<RouterA> system-view

[RouterA] multicast routing

[RouterA-mrib] quit

# Enable IGMP on GigabitEthernet 1/0/1.

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] igmp enable

[RouterA-GigabitEthernet1/0/1] quit

# Enable PIM-DM on GigabitEthernet 1/0/2.

[RouterA] interface gigabitethernet 1/0/2

[RouterA-GigabitEthernet1/0/2] pim dm

[RouterA-GigabitEthernet1/0/2] quit

3.     Configure Switch A:

# Enable IGMP snooping globally.

<SwitchA> system-view

[SwitchA] igmp-snooping

[SwitchA-igmp-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/3 to the VLAN.

[SwitchA] vlan 100

[SwitchA-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/3

# Enable IGMP snooping for VLAN 100.

[SwitchA-vlan100] igmp-snooping enable

[SwitchA-vlan100] quit

# Configure GigabitEthernet 1/0/3 as a static router port for VLAN 100.

[SwitchA] interface gigabitethernet 1/0/3

[SwitchA-GigabitEthernet1/0/3] igmp-snooping static-router-port vlan 100

[SwitchA-GigabitEthernet1/0/3] quit

4.     Configure Switch B:

# Enable IGMP snooping globally.

<SwitchB> system-view

[SwitchB] igmp-snooping

[SwitchB-igmp-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 to the VLAN.

[SwitchB] vlan 100

[SwitchB-vlan100] port gigabitethernet 1/0/1 gigabitethernet 1/0/2

# Enable IGMP snooping for VLAN 100.

[SwitchB-vlan100] igmp-snooping enable

[SwitchB-vlan100] quit

5.     Configure Switch C:

# Enable IGMP snooping globally.

<SwitchC> system-view

[SwitchC] igmp-snooping

[SwitchC-igmp-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/5 to the VLAN.

[SwitchC] vlan 100

[SwitchC-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/5

# Enable IGMP snooping for VLAN 100.

[SwitchC-vlan100] igmp-snooping enable

[SwitchC-vlan100] quit

# Configure GigabitEthernet 1/0/3 and GigabitEthernet 1/0/5 as static member ports for multicast group 224.1.1.1.

[SwitchC] interface gigabitethernet 1/0/3

[SwitchC-GigabitEthernet1/0/3] igmp-snooping static-group 224.1.1.1 vlan 100

[SwitchC-GigabitEthernet1/0/3] quit

[SwitchC] interface gigabitethernet 1/0/5

[SwitchC-GigabitEthernet1/0/5] igmp-snooping static-group 224.1.1.1 vlan 100

[SwitchC-GigabitEthernet1/0/5] quit

Verifying the configuration

# Display static router port information for VLAN 100 on Switch A.

[SwitchA] display igmp-snooping static-router-port vlan 100

VLAN 100:

  Router slots (0 in total):

  Router ports (1 in total):

    GE1/0/3

The output shows that GigabitEthernet 1/0/3 on Switch A has become a static router port.

# Display static IGMP snooping forwarding entries for VLAN 100 on Switch C.

[SwitchC] display igmp-snooping static-group vlan 100

Total 1 entries.

 

VLAN 100: Total 1 entries.

  (0.0.0.0, 224.1.1.1)

    Host slots (0 in total):

    Host ports (2 in total):

      GE1/0/3

      GE1/0/5

The output shows that GigabitEthernet 1/0/3 and GigabitEthernet 1/0/5 on Switch C have become static member ports of multicast group 224.1.1.1.

IGMP snooping querier configuration example

Network requirements

As shown in Figure 5:

·     The network is a Layer 2-only network.

·     Source 1 and Source 2 send multicast data to multicast groups 224.1.1.1 and 225.1.1.1, respectively.

·     Host A and Host C are receivers of multicast group 224.1.1.1, and Host B and Host D are receivers of multicast group 225.1.1.1.

·     All host receivers run IGMPv2, and all switches run IGMPv2 snooping. Switch A (which is close to the multicast sources) acts as the IGMP snooping querier.

Configure the switches to meet the following requirements:

·     To prevent the switches from flooding unknown packets in the VLAN, enable all the switches to drop unknown multicast data packets.

·     A switch does not mark a port that receives an IGMP query with source IP address 0.0.0.0 as a dynamic router port. This adversely affects the establishment of Layer 2 forwarding entries and multicast traffic forwarding. To avoid this, configure the source IP address of IGMP queries as a non-zero IP address.

Figure 5 Network diagram

 

Configuration procedure

1.     Configure Switch A:

# Enable IGMP snooping globally.

<SwitchA> system-view

[SwitchA] igmp-snooping

[SwitchA-igmp-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/3 to the VLAN.

[SwitchA] vlan 100

[SwitchA-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/3

# Enable IGMP snooping, and enable dropping unknown multicast data packets for VLAN 100.

[SwitchA-vlan100] igmp-snooping enable

[SwitchA-vlan100] igmp-snooping drop-unknown

# Configure Switch A as the IGMP snooping querier.

[SwitchA-vlan100] igmp-snooping querier

[SwitchA-vlan100] quit

# In VLAN 100, configure the source IP address of IGMP general queries and IGMP group-specific queries as 192.168.1.1.

[SwitchA-vlan100] igmp-snooping general-query source-ip 192.168.1.1

[SwitchA-vlan100] igmp-snooping special-query source-ip 192.168.1.1

[SwitchA-vlan100] quit

2.     Configure Switch B:

# Enable IGMP snooping globally.

<SwitchB> system-view

[SwitchB] igmp-snooping

[SwitchB-igmp-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/4 to the VLAN.

[SwitchB] vlan 100

[SwitchB-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/4

# Enable IGMP snooping, and enable dropping unknown multicast packets for the VLAN 100.

[SwitchB-vlan100] igmp-snooping enable

[SwitchB-vlan100] igmp-snooping drop-unknown

[SwitchB-vlan100] quit

3.     Configure Switch C:

# Enable IGMP snooping globally.

<SwitchC> system-view

[SwitchC] igmp-snooping

[SwitchC-igmp-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/3 to the VLAN.

[SwitchC] vlan 100

[SwitchC-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/3

# Enable IGMP snooping, and enable dropping unknown multicast data packets for VLAN 100.

[SwitchC-vlan100] igmp-snooping enable

[SwitchC-vlan100] igmp-snooping drop-unknown

[SwitchC-vlan100] quit

4.     Configure Switch D:

# Enable IGMP snooping globally.

<SwitchD> system-view

[SwitchD] igmp-snooping

[SwitchD-igmp-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 to the VLAN.

[SwitchD] vlan 100

[SwitchD-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/2

# Enable IGMP snooping, and enable dropping unknown multicast data packets for VLAN 100.

[SwitchD-vlan100] igmp-snooping enable

[SwitchD-vlan100] igmp-snooping drop-unknown

[SwitchD-vlan100] quit

Verifying the configuration

# Display statistics for IGMP messages learned through IGMP snooping on Switch B.

[SwitchB] display igmp-snooping statistics

Received IGMP general queries:  3

Received IGMPv1 reports:  0

Received IGMPv2 reports:  12

Received IGMP leaves:  0

Received IGMPv2 specific queries:  0

Sent     IGMPv2 specific queries:  0

Received IGMPv3 reports:  0

Received IGMPv3 reports with right and wrong records:  0

Received IGMPv3 specific queries:  0

Received IGMPv3 specific sg queries:  0

Sent     IGMPv3 specific queries:  0

Sent     IGMPv3 specific sg queries:  0

Received error IGMP messages:  0

The output shows that all switches except Switch A can receive the IGMP general queries after Switch A acts as the IGMP snooping querier.

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 it 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.