Table of Contents

Chapter 1 IGMP Snooping Configuration. 1-1

1.1 IGMP Snooping Overview. 1-1

1.1.1 Principle of IGMP Snooping. 1-1

1.1.2 Basic Concepts in IGMP Snooping. 1-2

1.1.3 Work Mechanism of IGMP Snooping. 1-3

1.2 IGMP Snooping Configuration Tasks. 1-5

1.3 Configuring Basic Functions of IGMP Snooping. 1-6

1.3.1 Configuration Prerequisites. 1-6

1.3.2 Enabling IGMP Snooping. 1-6

1.3.3 Configuring the Version of IGMP Snooping. 1-7

1.3.4 Configuring Port Aging Timers. 1-8

1.4 Configuring Port Functions. 1-9

1.4.1 Configuration Prerequisites. 1-9

1.4.2 Configuring Static Ports. 1-9

1.4.3 Enabling the Function of Simulating Member Hosts. 1-10

1.4.4 Enabling the Fast Leave Feature. 1-11

1.4.5 Configuring IGMP Report Suppression. 1-12

1.5 Configuring IGMP-Related Functions. 1-13

1.5.1 Configuration Prerequisites. 1-13

1.5.2 Enabling IGMP Snooping Querier 1-13

1.5.3 Configuring IGMP Timers. 1-14

1.5.4 Configuring Source IP Address of IGMP Queries. 1-15

1.5.5 Configuring the Function of Dropping Unknown Multicast Data. 1-16

1.6 Configuring a Multicast Group Policy. 1-16

1.6.1 Configuration Prerequisites. 1-16

1.6.2 Configuring a Multicast Group Filter 1-16

1.6.3 Configuring Multicast Source Port Filtering. 1-17

1.6.4 Configuring Maximum Multicast Groups that Can Pass Ports. 1-18

1.6.5 Configuring Multicast Group Replacement 1-19

1.7 Displaying and Maintaining IGMP Snooping. 1-20

1.8 IGMP Snooping Configuration Examples. 1-21

1.8.1 Simulating Member Hosts. 1-21

1.8.2 Static Router Port Configuration. 1-23

1.9 Troubleshooting IGMP Snooping Configuration. 1-25

1.9.1 Switch Fails in Layer 2 Multicast Forwarding. 1-25

1.9.2 Configured Multicast Group Policy Fails to Take Effect 1-25

Chapter 2 MLD Snooping Configuration. 2-1

2.1 MLD Snooping Overview. 2-1

2.1.1 How MLD Snooping Works. 2-1

2.1.2 Basic Concepts in MLD Snooping. 2-2

2.1.3 Work Mechanism of MLD Snooping. 2-3

2.2 MLD Snooping Configuration Tasks. 2-5

2.3 Configuring Basic Functions of MLD Snooping. 2-6

2.3.1 Configuration Prerequisites. 2-6

2.3.2 Enabling MLD Snooping. 2-6

2.3.3 Configuring Port Aging Timers. 2-7

2.4 Configuring Port Functions. 2-8

2.4.1 Configuration Prerequisites. 2-8

2.4.2 Configuring Static Ports. 2-8

2.4.3 Enabling the Function of Simulating Member Hosts. 2-9

2.4.4 Configuring the Fast Leave Feature. 2-10

2.4.5 Configuring MLD Report Suppression. 2-11

2.5 Configuring MLD-Related Functions. 2-11

2.5.1 Configuration Prerequisites. 2-11

2.5.2 Enabling MLD Snooping Querier 2-12

2.5.3 Configuring MLD Timers. 2-12

2.5.4 Configuring Source IPv6 Addresses of MLD Queries. 2-14

2.5.5 Configuring the Function of Dropping Unknown IPv6 Multicast Data. 2-14

2.6 Configuring an IPv6 Multicast Group Policy. 2-15

2.6.1 Configuration Prerequisites. 2-15

2.6.2 Configuring an IPv6 Multicast Group Filter 2-15

2.6.3 Configuring IPv6 Multicast Source Port Filtering. 2-16

2.6.4 Configuring Maximum Multicast Groups that Can Pass Ports. 2-17

2.6.5 Configuring IPv6 Multicast Group Replacement 2-18

2.7 Displaying and Maintaining MLD Snooping. 2-19

2.8 MLD Snooping Configuration Examples. 2-20

2.8.1 Simulated Host Joining. 2-20

2.8.2 Static Router Port Configuration. 2-22

2.9 Troubleshooting MLD Snooping. 2-23

2.9.1 Switch Fails in Layer 2 Multicast Forwarding. 2-23

2.9.2 Configured IPv6 Multicast Group Policy Fails to Take Effect 2-24

Chapter 3 Multicast VLAN Configuration. 3-1

3.1 Introduction to Multicast VLAN. 3-1

3.2 Configuring Multicast VLAN. 3-1

3.3 Displaying and Maintaining Multicast VLAN. 3-2

3.4 Multicast VLAN Configuration Example. 3-2

 

Chapter 1  IGMP Snooping Configuration

When configuration IGMP Snooping, go to the following sections for information you are interested in:

l           IGMP Snooping Overview

l           Configuring Basic Functions of IGMP Snooping

l           Configuring Port Functions

l           Configuring IGMP-Related Functions

l           Configuring a Multicast Group Policy

l           Displaying and Maintaining IGMP Snooping

l           IGMP Snooping Configuration Examples

l           Troubleshooting IGMP Snooping Configuration

1.1  IGMP Snooping Overview

Internet Group Management Protocol Snooping (IGMP Snooping) is a multicast constraining mechanism that runs on Layer 2 devices to manage and control multicast groups.

1.1.1  Principle of IGMP Snooping

By analyzing received IGMP messages, a Layer 2 device running IGMP Snooping establishes mappings between ports and MAC multicast groups and forwards multicast data based on these mappings.

As shown in Figure 1-1, when IGMP Snooping is not running, multicast packets are broadcast to all devices at Layer 2. When IGMP Snooping runs, multicast packets for known multicast groups are multicast to the receivers at Layer 2.

Figure 1-1 Multicast forwarding before and after IGMP Snooping runs

1.1.2  Basic Concepts in IGMP Snooping

I. IGMP Snooping related ports

As shown in Figure 1-2, Router A connects to the multicast source, IGMP Snooping runs on Switch A and Switch B, Host A and Host C are receiver hosts (namely, multicast group members).

Figure 1-2 IGMP Snooping related ports

Ports involved in IGMP Snooping, as shown in Figure 1-2, are described as follows:

l           Router port: On an Ethernet switch, a router port connects the switch to a multicast router. In the figure, GigabitEthernet1/0/1 of Switch A and GigabitEthernet1/0/1 of Switch B are router ports. A switch registers all its local router ports in its router port list.

l           Member port: On an Ethernet switch, a member port (also known as multicast group member port) connects the switch to a multicast group member. In the figure, GigabitEthernet1/0/2 and GigabitEthernet1/0/3 of Switch A and GigabitEthernet1/0/2 of Switch B are member ports. The switch records all member ports on the local device in the IGMP Snooping forwarding table.

 

 

II. Port aging timers in IGMP Snooping and related messages and actions

Table 1-1 Port aging timers in IGMP Snooping and related messages and actions

Timer	Description	Message before expiry	Action after expiry
Router port aging timer	For each router port, the switch sets a timer initialized to the aging time of the route port	IGMP general query or PIM hello message of which the source address is not 0.0.0.0	The switch removes this port from its router port list
Member port aging timer	When a port joins an multicast group, the switch sets a timer for the port, which is initialized to the member port aging time	IGMP report message	The switch removes this port from the multicast group forwarding table

 

1.1.3  Work Mechanism of IGMP Snooping

A switch running IGMP Snooping performs different actions when it receives different IGMP messages, as follows:

I. General queries

The IGMP querier periodically sends IGMP general queries to all hosts and routers on the local subnet to find out whether multicast group members exist on the subnet.

Upon receiving an IGMP general query, the switch forwards it through all ports in the VLAN except the receiving port and performs the following to the receiving port:

l           If the receiving port is a router port existing in its router port list, the switch resets the aging timer of this router port.

l           If the receiving port is not a router port existing in its router port list, the switch adds it into its router port list and sets an aging timer for this router port.

II. Membership reports

A host sends an IGMP report to the multicast router in the following circumstances:

l           Upon receiving an IGMP query, a multicast group member host responds with an IGMP report.

l           When intended to join a multicast group, a host sends an IGMP report to the multicast router to announce that it is to join the multicast group.

Upon receiving the IGMP report, the switch forwards it through all the router ports in the VLAN and performs the following to the receiving port:

l           Resolves the address of the multicast group that the host is to join and add a forwarding entry for this port in the forwarding table.

l           Sets or resets a member port aging timer for this port.

 

 

III. Leave messages

When an IGMPv1 host leaves a multicast group, the host does not send an IGMP leave message, so the switch cannot know immediately that the host has left the multicast group. However, as the host stops sending IGMP reports as soon as it leaves a multicast group, the switch deletes the forwarding entry for the member port corresponding to the host from the forwarding table when its aging timer expires.

When an IGMPv2 or IGMPv3 host leaves a multicast group, the host sends an IGMP leave message to the multicast router to announce that it has leaf the multicast group.

Upon receiving an IGMP leave message on the last member port, a switch forwards it out all router ports in the VLAN. Because the switch does not know whether any other member hosts of that multicast group still exists under the port to which the IGMP leave message arrived, the switch does not immediately delete the forwarding entry corresponding to that port from the forwarding table; instead, it resets the aging timer of the member port.

Upon receiving the IGMP leave message from a host, the IGMP querier resolves from the message the address of the multicast group that the host just left and sends an IGMP group-specific query to that multicast group through the port that received the leave message. Upon receiving the IGMP group-specific query, a switch forwards it through all the router ports in the VLAN and all member ports of that multicast group, and performs the following to the receiving port:

l           If a response to an IGMP report from that multicast group arrives to the member port before its aging timer expires, this means that some other members of that multicast group still exist under that port: the switch resets the aging timer of the member port.

l           If no IGMP report from that multicast group arrives to this member port before its aging timer expires as a response to the IGMP group-specific query,this means that no members of that multicast group still exist under the port: the switch deletes the forwarding entry corresponding to the port from the forwarding table when the aging timer expires.

1.2  IGMP Snooping Configuration Tasks

Complete these tasks to configure IGMP Snooping:

Task		Remarks
Configuring Basic Functions of IGMP Snooping	Enabling IGMP Snooping	Required
	Configuring the Version of IGMP Snooping	Optional
	Configuring Port Aging Timers	Optional
Configuring Port Functions	Configuring Static Ports	Optional
	Enabling the Function of Simulating Member Hosts	Optional
	Enabling the Fast Leave Feature	Optional
	Configuring IGMP Report Suppression	Optional
Configuring IGMP-Related Functions	Enabling IGMP Snooping Querier	Optional
	Configuring IGMP Timers	Optional
	Configuring Source IP Address of IGMP Queries	Optional
	Configuring the Function of Dropping Unknown Multicast Data	Optional
Configuring a Multicast Group Policy	Configuring a Multicast Group Filter	Optional
	Configuring Multicast Source Port Filtering	Optional
	Configuring Maximum Multicast Groups that Can Pass Ports	Optional
	Configuring Multicast Group Replacement	Optional

 

 

1.3  Configuring Basic Functions of IGMP Snooping

1.3.1  Configuration Prerequisites

Before configuring the basic functions of IGMP Snooping, complete the following tasks:

l           Configure the corresponding VLANs

l           Configure the corresponding port groups

Before configuring the basic functions of IGMP Snooping, prepare the following data:

l           Version of IGMP Snooping

l           Aging time of router ports

l           Aging timer of member ports

1.3.2  Enabling IGMP Snooping

Follow these steps to enabling IGMP Snooping:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enable IGMP Snooping globally and enter IGMP Snooping view	igmp-snooping	Required Disabled by default
Return to system view	quit	—
Enter VLAN view	vlan vlan-id	—
Enable IGMP Snooping in the VLAN	igmp-snooping enable	Required Disabled by default

 

 

1.3.3  Configuring the Version of IGMP Snooping

By configuring the IGMP Snooping version, you are actually configuring the version of IGMP messages that can be analyzed and processed by IGMP Snooping.

l           In the case of version 2, IGMP Snooping can analyze and process IGMPv1 and IGMPv2 messages, but not IGMPv3 messages, which will be broadcast in the VLAN.

l           If the current is 3, IGMP Snooping can analyze and process IGMPv1, IGMPv2 and IGMPv3 messages.

Follow these steps to configure the version of IGMP Snooping:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure the version of IGMP Snooping	igmp-snooping version version-number	Optional Version 2 by default

 

 

1.3.4  Configuring Port Aging Timers

If the switch does not receive an IGMP general query or a PIM hello message before the aging timer of a router port expires, the switch deletes this port from the router port list when the aging timer times out.

If the switch does not receive an IGMP report from a multicast group before the aging timer of a member port expires, the switch deletes this port from the forwarding table for that multicast group when the aging timers times out.

If multicast group memberships change frequently, you can set a relatively small value for the member port aging timer, and vice versa.

I. Configuring port aging timers globally

Follow these steps to configure port aging timers globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Configure router port aging time	router-aging-time interval	Optional 105 seconds by default
Configure member port aging time	host-aging-time interval	Optional 260 seconds by default

 

II. Configuring port aging timers in a VLAN

Follow these steps to configure port aging timers in a VLAN:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure router port aging time	igmp-snooping router-aging-time interval	Optional 105 seconds by default
Configure member port aging time	igmp-snooping host-aging-time interval	Optional 260 seconds by default

 

1.4  Configuring Port Functions

1.4.1  Configuration Prerequisites

Before configuring port functions, complete the following task:

l           Enable IGMP Snooping in the VLAN

Before configuring port functions, prepare the following data:

l           Multicast group and multicast source addresses

l           Whether to enable the fast leave feature

l           Whether to enabled IGMP report suppression

1.4.2  Configuring Static Ports

If the host attached to a port needs to receive multicast data addressed to a particular multicast group or from a particular multicast source/group, you can configure this port to be a static member port of that multicast group or multicast source/group.

In a network with a stable topology structure, you can configure router ports of a switch into static router ports, through which the switch can receive IGMP messages from routers.

Follow these steps to configure static ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure a static member port		igmp-snooping static-group group-address [ source-ip source_address ] vlan vlan-id	Required Disabled by default
Configuring a static router port		igmp-snooping static-router-port vlan vlan-id	Required Disabled by default

 

 

1.4.3  Enabling the Function of Simulating Member Hosts

Generally, a host running IGMP responds to IGMP queries from a multicast router. If a host fails to respond due to some reasons, the multicast router will deem that no member of this multicast group exists on the network segment, and therefore will remove the corresponding forwarding path.

To avoid this situation from happening, you can configure a port of the switch as a member of the multicast group(namely, enable the function of simulating member hosts on the port). When an IGMP query arrives, that member port will give a response. As a result, the switch can continue receive multicast data.

Through this configuration, the following functions can be implemented:

l           When the function of simulating member hosts is enabled on an Ethernet port, the simulated host sends an IGMP report.

l           When receiving an IGMP general query, the simulated host responds with an IGMP report just like a real host.

l           When the function of simulating member hosts is disabled on an Ether port, the simulated host sends an IGMP leave message.

Follow these steps to enable the function of simulating member hosts:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Enable the function of simulating a member host of a multicast group or multicast source/group		igmp-snooping host-join group-address [ source-ip source-address ] vlan vlan-id	Required Disabled by default

 

 

1.4.4  Enabling the Fast Leave Feature

By default, when receiving a group-specific IGMP leave message on a port, the switch first sends an IGMP group-specific query message that port, rather than directly deleting the port from the multicast forwarding table. If the switch receives no response within a certain period of waiting time, it deletes the port from the forwarding table.

With the fast leave feature enabled, when the switch receives a group-specific IGMP leave message on a port, the switch directly deletes this port from the forwarding table without first sending an IGMP group-specific query to the port.

I. Configuring the fast leave feature globally

Follow these steps to configure the fast leave feature globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Enable the fast leave feature	fast-leave [ vlan vlan-list ]	Required Disabled by default

 

II. Configuring the fast leave feature on a port or a group ports

Follow these steps to configure the fast leave feature on a port or a group ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Enable the fast leave feature		igmp-snooping fast-leave [ vlan vlan-list ]	Required Disabled by default

 

 

1.4.5  Configuring IGMP Report Suppression

When a Layer 2 device receives an IGMP report from a multicast group member, the device forwards the message to the Layer 3 device directly connected with it. Thus, when multiple members belonging to a multicast group exit on the Layer 2 device, the Layer 3 device directly connected with it will receive duplicate IGMP reports from these members.

With the IGMP report suppression function enabled, within a query interval, the Layer 2 device forwards only the first IGMP report of a multicast group to the Layer 3 device and will not forward the subsequent IGMP reports from the same multicast group to the Layer 3 device. This helps reduce the number of packets being transmitted over the network.

Follow these steps to configure IGMP report suppression:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Enable IGMP report suppression	report-aggregation	Optional Enabled by default

 

1.5  Configuring IGMP-Related Functions

1.5.1  Configuration Prerequisites

Before configuring IGMP-related functions, complete the following task:

l           Enable IGMP Snooping in the VLAN

Before configuring IGMP-related functions, prepare the following data:

l           IGMP general query interval

l           IGMP last-member query interval

l           Maximum response time to IGMP general queries

l           Source address of IGMP general queries

l           Source address of IGMP group-specific queries

l           Whether to enable the function of dropping unknown multicast data

1.5.2  Enabling IGMP Snooping Querier

In an IP multicast network running IGMP, a Layer 3 multicast device acts as the IGMP querier, responsible for sending IGMP queries.

In a network that does not comprise Layer 3 multicast devices, however, it is a problem to implement an IGMP querier, because Layer 2 device do not support IGMP. To solve this problem, you can enable the IGMP Snooping querier function on a Layer 2 device so that it can work as an IGMP querier to create and maintain multicast forwarding entries at the data link layer.

Follow these steps to enable IGMP Snooping querier:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Enable IGMP Snooping querier	igmp-snooping querier	Required Disabled by default

 

 

1.5.3  Configuring IGMP Timers

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

Upon receiving an IGMP query (general query or group-specific query), a host starts a timers for each multicast group it has joined. This timer is initialized to a random value in the range of 0 to the maximum response time (the host obtains the value of the maximum response time from the Max Response Time field in the IGMP query it received). When the timer value comes down to 0, the host sends an IGMP report to the corresponding multicast group.

An appropriate setting of the maximum response time for IGMP queries allows hosts to respond to queries quickly and avoids burstiness of IGMP traffic on the network caused by reports simultaneously sent by a large number of hosts when corresponding timers expires simultaneously.

l           For IGMP general queries, you can configure the maximum response time to fill their Max Response time field.

l           For IGMP group-specific queries, you can configure the IGMP last-member query interval to fill their Max Response time field. Namely, for IGMP group-specific queries, the maximum response time equals to the IGMP last-member query interval.

I. Configuring IGMP timers globally

Follow these steps to configure IGMP timers globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Configure the maximum response time to IGMP general queries	max-response-time interval	Optional 10 seconds by default
Configure the IGMP last-member query interval	last-member-query-interval interval	Optional 1 second by default

 

II. Configuring IGMP timers in a VLAN

Follow these steps to configure IGMP timers in a VLAN:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure IGMP general query interval	igmp-snooping query-interval interval	Optional 60 second by default
Configure the maximum response time to IGMP general queries	igmp-snooping max-response-time interval	Optional 10 seconds by default
Configure the IGMP last-member query interval	igmp-snooping last-member-query-interval interval	Optional 1 second by default

 

 

1.5.4  Configuring Source IP Address of IGMP Queries

Upon receiving an IGMP query whose source IP address is 0.0.0.0 on a port, the switch will not set that port as a router port. Therefore, we recommend that you configure a valid IP address as the source IP address of IGMP queries.

Follow these steps to configure source IP address of IGMP queries:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure the source address of IGMP general queries	igmp-snooping general-query source-ip { current-interface | ip-address }	Optional 0.0.0.0 by default
Configure the source IP address of IGMP group-specific queries	igmp-snooping special-query source-ip { current-interface | ip-address }	Optional 0.0.0.0 by default

 

 

1.5.5  Configuring the Function of Dropping Unknown Multicast Data

Unknown multicast data refers to multicast data whose forwarding entries do not exist in the corresponding multicast forwarding table.

Follow these steps to configure the function of dropping unknown multicast data in a VLAN:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Enable the function of dropping unknown multicast data	igmp-snooping drop-unknown	Required Disabled by default

 

 

1.6  Configuring a Multicast Group Policy

1.6.1  Configuration Prerequisites

Before configuring a multicast group filtering policy, complete the following task:

l           Enable IGMP Snooping in the VLAN or enable IGMP on the desired VLAN interface

Before configuring a multicast group filtering policy, prepare the following data:

l           ACL rule for multicast group filtering

l           Whether to enable multicast source port filtering

l           The maximum number of multicast groups that can pass the ports

l           Whether to enable multicast group replacement

1.6.2  Configuring a Multicast Group Filter

On an IGMP Snooping–enabled switch, the configuration of a multicast group allows the service provider to define limits of multicast programs available to different users.

In actual application, when a user requests a multicast program, the user’s host initiates an IGMP report. After the message reaches the switch, the switch checks the report against the ACL rule configured on the receiving port. If the receiving port can join this multicast group, the switch adds this port to the IGMP Snooping multicast group list; otherwise the switch drops this report message. Thus, the multicast data will not be sent to this port. In this way, the service provider can control the VOD programs provided for multicast users.

I. Configuring a multicast group filter globally

Follow these steps to configure a multicast group filter globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Configure a multicast group filter	group-policy acl-number [ vlan vlan-list ]	Required No filter configured by default

 

II. Configuring a multicast group filter on a port or a group ports

Follow these steps to configuring a multicast group filter on a port or a group ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure a multicast group filter		igmp-snooping group-policy acl-number [ vlan vlan-list ]	Required No filter configured by default

 

1.6.3  Configuring Multicast Source Port Filtering

With the multicast source port filtering feature enabled, you can enable or disable a port as a multicast source port.

l           If this feature is enabled on a port, the port can be connected with multicast receivers only rather than with multicast sources, because the port will block all multicast data packets while it permits multicast protocol packets to pass.

l           If this feature is disabled on a port, the port can be connected with both multicast sources and multicast receivers.

I. Configuring multicast source port filtering globally

Follow these steps to configure multicast source port filtering globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Enable multicast source port filtering	source-deny port interface-list	Required Disabled by default

 

II. Configuring multicast source port filtering on a port or a group ports

Follow these steps to configure multicast source port filtering on a port or a group ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Enable multicast source port filtering		igmp-snooping source-deny	Required Disabled by default

 

 

1.6.4  Configuring Maximum Multicast Groups that Can Pass Ports

By configuring the maximum number of multicast groups that can pass a port or a group of ports, you can limit the number of number of multicast programs on-demand available to users, thus to control the traffic on the port.

Follow these steps to configure the maximum number of multicast groups that can pass the port(s):

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure the maximum number of multicast groups that can pass the port(s)		igmp-snooping group-limit limit [ vlan vlan-list ]	Optional 128 by default

 

 

1.6.5  Configuring Multicast Group Replacement

For some special reasons, the number of multicast groups passing through a switch or Ethernet port may exceed the number configured for the switch or the port. To address this situation, you can enable the multicast group replacement function on the switch or certain Ethernet ports. When the number of multicast groups an Ethernet port has joined reaches the limit,

l           If the multicast group replacement is enabled, the newly joined multicast group automatically replaces an existing multicast group with the lowest address.

l           If the multicast group replacement is not enabled, new IGMP reports will be automatically discarded.

I. Configuring multicast group replacement globally

Follow these steps to configure multicast group replacement globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Configure multicast group replacement	overflow-replace [ vlan vlan-list ]	Required Disabled by default

 

II. Configuring multicast group replacement on a port or a group port

Follow these steps to configure multicast group replacement on a port or a group ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure multicast group replacement		igmp-snooping overflow-replace [ vlan vlan-list ]	Required Disabled by default

 

1.7  Displaying and Maintaining IGMP Snooping

To do...	Use the command...	Remarks
View the information of multicast groups learned by IGMP Snooping	display igmp-snooping group [ vlan vlan-id ] [ verbose ]	Available in any view
View the statistics information of IGMP messages learned by IGMP Snooping	display igmp-snooping statistics	Available in any view
Clear IGMP Snooping entries	reset igmp-snooping group { group-address | all } [ vlan vlan-id ]	Available in user view
Clear the statistics information of all kinds of IGMP messages learned by IGMP Snooping	reset igmp-snooping statistics	Available in user view

 

 

1.8  IGMP Snooping Configuration Examples

1.8.1  Simulating Member Hosts

I. Network requirements

After the configuration, Host A and Host B, regardless of whether they have joined the multicast group 224.1.1.1, can receive multicast data that the multicast source 1.1.1.1/24 sends to the multicast group 224.1.1.1. Figure 1-3 shows the network connections.

II. Network diagram

Figure 1-3 Network diagram for simulated member host configuration

III. Configuration procedure

1)         Configuring a VLAN

# Create VLAN 100.

<SwitchA> system-view

[SwitchA] vlan 100

# Add ports GigabitEthernet1/01 through GigabitEthernet1/0/4 into VLAN 100.

[SwitchA-vlan100] port GigabitEthernet 1/0/1 to GigabitEthernet1/0/4

[SwitchA-vlan100] quit

2)         Enabling the function of simulating member hosts of a multicast source/group

# Enable IGMP Snooping in VLAN 100, and set its version to 3.

[SwitchA] igmp-snooping

[SwitchA-igmp-snooping] quit

[SwitchA] vlan 100

[SwitchA-vlan100] igmp-snooping enable

[SwitchA-vlan100] igmp-snooping version 3

[SwitchA-vlan100] quit

# Enable the simulated host to join the multicast source/group on GigabitEthernet1/0/3 and GigabitEthernet1/0/3 respectively.

[SwitchA] interface GigabitEthernet1/0/3

[SwitchA- GigabitEthernet1/0/3] igmp-snooping host-join 224.1.1.1 source-ip 1.1.1.1 vlan 100

[SwitchA- GigabitEthernet1/0/3] quit

[SwitchA] interface GigabitEthernet 1/0/4

[SwitchA- GigabitEthernet 1/0/4] igmp-snooping host-join 224.1.1.1 source-ip 1.1.1.1 vlan 100

[SwitchA- GigabitEthernet 1/0/4] quit

3)         Verifying the configuration

# View the detailed information of the multicast group in VLAN 100.

[SwitchA] display igmp-snooping group vlan 100 verbose

    Total 1 IP Group(s).

    Total 1 IP Source(s).

    Total 1 MAC Group(s).

 

  Port flags: D-Dynamic port, S-Static port, A-Aggregation port, C-Copy port

  Subvlan flags: R-Real VLAN, C-Copy VLAN

  Vlan(id):100.

    Total 1 IP Group(s).

    Total 1 IP Source(s).

    Total 1 MAC Group(s).

    Router port(s):total 1 port.

            GigabitEthernet 1/0/1                                   (D) ( 00:01:30 )

    IP group(s):the following ip group(s) match to one mac group.

      IP group address:224.1.1.1

        (1.1.1.1, 224.1.1.1):

          Attribute:    Host Port

          Host port(s):total 2 port.

            GigabitEthernet 1/0/3                                   (D) ( 00:03:23 )

            GigabitEthernet 1/0/4                                    (D) ( 00:03:23 )

    MAC group(s):

      MAC group address:0100-5e01-0101

          Host port(s):total 2 port.

            GigabitEthernet 1/0/3

            GigabitEthernet 1/0/4

As shown above, GigabitEthernet 1/0/3 and GigabitEthernet 1/0/4 of Switch A have joined multicast source/group (1.1.1.1, 224.1.1.1).

1.8.2  Static Router Port Configuration

I. Network requirements

No multicast protocol is running on Router B. After the configuration, Switch A should be able to forward multicast data to Router B. Figure 1-4 shows the routernetwork connections.

II. Network diagram

Figure 1-4 Network diagram for static router port configuration

III. Configuration procedure

1)         Configuring a VLAN

# Create VLAN 100.

<SwitchA> system-view

[SwitchA] vlan 100

# Add ports GigabitEthernet1/0/1 through GigabitEthernet1/0/4 into VLAN 100.

[SwitchA-vlan100] port GigabitEthernet1/0/1 to GigabitEthernet1/0/4

[SwitchA-vlan100] quit

2)         Configuring a static router port

# Enable IGMP Snooping in VLAN 100.

[SwitchA] igmp-snooping

[SwitchA-igmp-snooping] quit

[SwitchA] vlan 100

[SwitchA-vlan100] igmp-snooping enable

[SwitchA-vlan100] quit

# Configure GigabitEthernet1/0/4 to be a static router port.

[SwitchA] interface GigabitEthernet1/0/4

[SwitchA- GigabitEthernet1/0/4] igmp-snooping static-router-port vlan 100

[SwitchA- GigabitEthernet1/0/4] quit

3)         Verifying the configuration

# View the detailed information of the multicast group in VLAN 100.

[SwitchA] display igmp-snooping group vlan 100 verbose

    Total 1 IP Group(s).

    Total 1 IP Source(s).

    Total 1 MAC Group(s).

 

  Port flags: D-Dynamic port, S-Static port, A-Aggregation port, C-Copy port

  Subvlan flags: R-Real VLAN, C-Copy VLAN

  Vlan(id):100.

    Total 1 IP Group(s).

    Total 1 IP Source(s).

    Total 1 MAC Group(s).

    Router port(s):total 2 port.

            GigabitEthernet1/0/1                                    (D) ( 00:01:30 )

            GigabitEthernet1/0/4                                    (S) ( 00:01:30 )

    IP group(s):the following ip group(s) match to one mac group.

      IP group address:224.1.1.1

        (1.1.1.1, 224.1.1.1):

          Attribute:    Host Port

          Host port(s):total 1 port.

            GigabitEthernet1/0/3                                    (D) ( 00:03:23 )

    MAC group(s):

      MAC group address:0100-5e01-0101

          Host port(s):total 1 port.

            GigabitEthernet1/0/3

As shown above, GigabitEthernet1/0/4 of Switch A has become a static router port.

1.9  Troubleshooting IGMP Snooping Configuration

1.9.1  Switch Fails in Layer 2 Multicast Forwarding

I. Symptom

A switch fails to implement Layer 2 multicast forwarding.

II. Analysis

IGMP Snooping is not enabled.

III. Solution

1)         Enter the display current-configuration command to view the running status of IGMP Snooping.

2)         If IGMP Snooping is not enabled, use the igmp-snooping command to enable IGMP Snooping globally and then use igmp-snooping enable command to enable IGMP Snooping in VLAN view.

3)         If IGMP Snooping is disabled only for the corresponding VLAN, just use the igmp-snooping enable command in VLAN view to enable IGMP Snooping in the corresponding VLAN.

1.9.2  Configured Multicast Group Policy Fails to Take Effect

I. Symptom

Although a multicast group policy has been configured to allow hosts to join specific multicast groups, the hosts can still receive multicast data addressed to other multicast groups.

II. Analysis

l           The ACL rule is incorrectly configured

l           The multicast group policy is not correctly applied

l           The function of dropping unknown multicast data is not enabled, so unknown multicast data is broadcast

l           Certain ports have been configured as static member ports of multicasts groups, and this configuration conflicts with the configured multicast group policy.

III. Solution

1)         Use the display acl command to check the configured ACL rule. Make sure that the ACL rule conforms to the multicast group policy to be implemented.

2)         Use the display this command to check whether the correct multicast group policy has been applied. If not, use the igmp-snooping group-policy command to apply the correct multicast group policy.

3)         Use the display current-configuration command to whether the function of dropping unknown multicast data is enabled. If not, use the drop-unknown or igmp-snooping drop-unknown command to enable the function of dropping unknown multicast data.

4)         Use the display igmp-snooping group command to check whether any port has been configured as a static member port of any multicast group. If so, check whether this configuration conflicts with the configured multicast group policy. If any conflict exists, remove the port as a static member of the multicast group.

 

Chapter 2  MLD Snooping Configuration

When configuring MLD Snooping, go to these sections for information you are interested in:

l           MLD Snooping Overview

l           Configuring Basic Functions of MLD Snooping

l           Configuring Port Functions

l           Configuring MLD-Related Functions

l           Configuring an IPv6 Multicast Group Policy

l           Displaying and Maintaining MLD Snooping

l           MLD Snooping Configuration Examples

l           Troubleshooting MLD Snooping

2.1  MLD Snooping Overview

Multicast Listener Discovery Snooping (MLD Snooping) is an IPv6 multicast constraining mechanism that runs on Layer 2 devices to manage and control IPv6 multicast groups.

2.1.1  How MLD Snooping Works

By analyzing received MLD messages, a Layer 2 device running MLD Snooping establishes mappings between ports and MAC multicast groups and forwards IPv6 multicast data based on these mappings.

As shown in Figure 2-1, when MLD Snooping is not running, IPv6 multicast packets are broadcast to all devices at Layer 2. When MLD Snooping runs, multicast packets for known IPv6 multicast groups are multicast to the receivers at Layer 2.

Figure 2-1 IPv6 multicast before and after MLD Snooping runs

2.1.2  Basic Concepts in MLD Snooping

I. MLD Snooping related ports

As shown in Figure 2-2, Router A connects to the multicast source, MLD Snooping runs on Switch A and Switch B, Host A and Host C are receiver hosts (namely, IPv6 multicast group members).

Figure 2-2 MLD Snooping related ports

Ports involved in MLD Snooping, as shown in Figure 2-2, are described as follows:

l           Router port: On an Ethernet switch, a router port connects the switch to a multicast router. In the figure, GigabitEthernet1/0/1 of Switch A and GigabitEthernet1/0/1 of Switch B are router ports. A switch registers all its local router ports in its router port list.

l           Member port: On an Ethernet switch, a member port (also known as IPv6 multicast group member port) connects the switch to an IPv6 multicast group member. In the figure, GigabitEthernet1/0/2 and GigabitEthernet1/0/3 of Switch A and GigabitEthernet1/0/2 of Switch B are member ports.The switch records all member ports on the local device in the MLD Snooping forwarding table.

 

 

II. Port aging timers in MLD Snooping

Table 2-1 Port aging timers in MLD Snooping and related messages and actions

Timer	Description	Message before expiry	Action after expiry
Router port aging timer	For each router port, the switch sets a timer initialized to the aging time of the route port	MLD general query or IPv6 PIM hello message of which the source address is not 0::0	The switch removes this port from its router port list
Member port aging timer	When a port joins an IPv6 multicast group, the switch sets a timer for the port, which is initialized to the member port aging time	MLD report message	The switch removes this port from the IPv6 multicast group forwarding table

 

2.1.3  Work Mechanism of MLD Snooping

A switch running MLD Snooping performs different actions when it receives different MLD messages, as follows:

I. General queries

The MLD querier periodically sends MLD general queries to all hosts and routers on the local subnet to find out whether IPv6 multicast group members exist on the subnet.

Upon receiving an MLD general query, the switch forwards it through all ports in the VLAN except the receiving port and performs the following to the receiving port:

l           If the receiving port is a router port existing in its router port list, the switch resets the aging timer of this router port.

l           If the receiving port is not a router port existing in its router port list, the switch adds it into its router port list and sets an aging timer for this router port.

II. Membership reports

A host sends an MLD report to the multicast router in the following circumstances:

l           Upon receiving an MLD query, an IPv6 multicast group member host responds with an MLD report.

l           When intended to join an IPv6 multicast group, a host sends an MLD report to the multicast router to announce that it is to join the IPv6 multicast group.

Upon receiving the MLD report, the switch forwards it through all the router ports in the VLAN and performs the following to the receiving port:

l           Resolves the address of the IPv6 multicast group that the host is to join and add a forwarding entry for this port in the forwarding table.

l           Sets or resets a member port aging timer for this port.

 

 

III. Done messages

When a host leaves an IPv6 multicast group, the host sends an MLD done message to the multicast router to announce that it is to leave the IPv6 multicast group.

Upon receiving an MLD done message, a switch forwards it through all router ports in the VLAN. Because the switch does not know whether any other member hosts of that IPv6 multicast group still exists under the port to which the MLD done message arrived, the switch does not immediately delete the forwarding entry corresponding to that port from the forwarding table; instead, it resets the aging timer of the member port.

Upon receiving an MLD done message from a host, the MLD querier resolves from the message the address of the IPv6 multicast group that the host just left and sends an MLD group-specific query to that IPv6 multicast group through the port that received the done message. Upon receiving the MLD group-specific query, a switch forwards it through all the router ports in the VLAN and all member ports of that IPv6 multicast group, and performs the following to the receiving port:

l           If an MLD report from that IPv6 multicast group arrives to this member port before its aging timer expires as a response to the MLD group-specific query , this means that some other members of that IPv6 multicast group still exist under the port: the switch resets the aging timer of the member port.

l           If no MLD report from that IPv6 multicast group arrives to this member port before its aging timer expires as a response to the MLD group-specific query , this means that no members of that IPv6 multicast group still exist under the member port: the switch deletes the forwarding entry for the member port from the forwarding table when its aging timer expires.

2.2  MLD Snooping Configuration Tasks

Complete these tasks to configure MLD Snooping:

Task		Remarks
Configuring Basic Functions of MLD Snooping	Enabling MLD Snooping	Required
	Configuring Port Aging Timers	Optional
Configuring Port Functions	Configuring Static Ports	Optional
	Enabling the Function of Simulating Member Hosts	Optional
	Configuring the Fast Leave Feature	Optional
	Configuring MLD Report Suppression	Optional
Configuring MLD-Related Functions	Enabling MLD Snooping Querier	Optional
	Configuring MLD Timers	Optional
	Configuring Source IPv6 Addresses of MLD Queries	Optional
	Configuring the Function of Dropping Unknown IPv6 Multicast Data	Optional
Configuring an IPv6 Multicast Group Policy	Configuring an IPv6 Multicast Group Filter	Optional
	Configuring IPv6 Multicast Source Port Filtering	Optional
	Configuring Maximum Multicast Groups that Can Pass Ports	Optional
	Configuring IPv6 Multicast Group Replacement	Optional

 

 

2.3  Configuring Basic Functions of MLD Snooping

2.3.1  Configuration Prerequisites

Before configuring the basic functions of MLD Snooping, complete the following tasks:

l           Configure the corresponding VLANs

l           Configure the corresponding port groups

Before configuring the basic functions of MLD Snooping, prepare the following data:

l           Aging time of router ports

l           Aging timer of member ports

2.3.2  Enabling MLD Snooping

Follow these steps to enable MLD Snooping:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enable MLD Snooping globally and enter MLD Snooping view	mld-snooping	Required Disabled by default
Return to system view	quit	—
Enter VLAN view	vlan vlan-id	—
Enable MLD Snooping in the VLAN	mld-snooping enable	Required Disabled by default

 

 

2.3.3  Configuring Port Aging Timers

If the switch does not receive an MLD general query or an IPv6 PIM hello message before the aging timer of a router port expires, the switch deletes this port from the router port list when the aging timer times out.

If the switch does not receive an MLD report from an IPv6 multicast group before the aging timer of a member port expires, the switch deletes this port from the forwarding table for that IPv6 multicast group when the aging timers times out.

If IPv6 multicast group memberships change frequently, you can set a relatively small value for the member port aging timer, and vice versa.

I. Configuring port aging timers globally

Follow these steps to configure port aging timers globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter MLD Snooping view	mld-snooping	—
Configure router port aging time	router-aging-time interval	Optional 260 seconds by default
Configure member port aging time	host-aging-time interval	Optional 260 seconds by default

 

II. Configuring port aging timers in a VLAN

Follow these steps to configure port aging timers in a VLAN:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure router port aging time	mld-snooping router-aging-time interval	Optional 260 seconds by default
Configure member port aging time	mld-snooping host-aging-time interval	Optional 260 seconds by default

 

2.4  Configuring Port Functions

2.4.1  Configuration Prerequisites

Before configuring port functions, complete the following tasks:

l           Enable MLD Snooping in the VLAN or enable MLD on the desired VLAN interface

Before configuring port functions, prepare the following data:

l           Address of IPv6 multicast group

l           Whether to enable the fast leave feature

l           Whether to enabled MLD report suppression

2.4.2  Configuring Static Ports

If the host attached to a port needs to receive IPv6 multicast data addressed to a particular IPv6 multicast group, you can configure this port to be a static member port of that IPv6 multicast group.

In a network with a stable topology structure, you can configure router ports of a switch into static router ports, through which the switch can receive MLD messages from routers or Layer 3 switches.

Follow these steps to configure static ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure a static member port		mld-snooping static-group ipv6-group-address vlan vlan-id	Required Disabled by default
Configure a static router port		mld-snooping static-router-port vlan vlan-id	Required Disabled by default

 

 

2.4.3  Enabling the Function of Simulating Member Hosts

Generally, a host running MLD responds to MLD queries from a multicast router. If a host fails to respond due to some reasons, the multicast router will deem that no member of this IPv6 multicast group exists on the network segment, and therefore will remove the corresponding forwarding path.

To avoid this situation from happening, you can configure a port of the switch as a member of the IPv6 multicast group (namely, enable the function of simulating a member host on the port). When an MLD query arrives, that member port will give a response. As a result, the switch can continue receive IPv6 multicast data.

Through this configuration, the following functions can be implemented:

l           When the function of simulating member hosts is enabled on an Ethernet port, the simulated host sends an MLD report.

l           When receiving an MLD general query, the simulated host responds with an MLD report just like a real host.

l           When the function of simulating member hosts is disabled on an Ethernet port, the simulated host sends an MLD done message.

Follow these steps to enable the function of simulating member hosts:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Enable the function of simulating a member host of an IPv6 multicast group		mld-snooping host-join ipv6-group-address vlan vlan-id	Required Disabled by default

 

 

2.4.4  Configuring the Fast Leave Feature

By default, when receiving a group-specific MLD done message on a port, the switch sends a MLD group-specific query message to that port rather than directly deleting the port from the multicast forwarding table. If the switch receives no response within a certain period of time, it deletes the port from the forwarding table.

With the fast leave feature enabled, when the switch receives a group-specific MLD done message on a port, the switch directly deletes this port from the forwarding table without first sending a MLD group-specific query to the port.

I. Configuring the fast leave feature globally

Follow these steps to configure the fast leave feature globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter MLD Snooping view	mld-snooping	—
Enable the fast leave feature	fast-leave [ vlan vlan-list ]	Required Disabled by default

 

II. Configuring the fast leave feature on a port or a group ports

Follow these steps to configure the fast leave feature on a port or a group ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Enable the fast leave feature		mld-snooping fast-leave [ vlan vlan-list ]	Required Disabled by default

 

 

2.4.5  Configuring MLD Report Suppression

When a Layer 2 device receives an MLD report from an IPV6 multicast group member, the Layer 2 device forwards the message to the Layer 3 device directly connected with it. Thus, when multiple members belonging to an IPv6 multicast group exit on the Layer 2 device, the Layer 3 device directly connected with it will receive duplicate MLD reports from these members.

With the MLD report suppression function enabled, within a query interval, the Layer 2 device forwards only the first MLD report of an IPv6 group to the Layer 3 device and will not forward the subsequent MLD reports from the same multicast group to the Layer 3 device. This helps reduce the number of packets being transmitted over the network.

Follow these steps to configure MLD report suppression:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter MLD Snooping view	mld-snooping	—
Enable MLD report suppression	report-aggregation	Optional Enabled by default

 

2.5  Configuring MLD-Related Functions

2.5.1  Configuration Prerequisites

Before configuring MLD-related functions, complete the following tasks:

l           Enable MLD Snooping in the VLAN

Before configuring MLD-related functions, prepare the following data:

l           MLD general query interval

l           MLD last-member query interval

l           Maximum response time for MLD general queries

l           Source IPv6 address of MLD general queries

l           Source IPv6 address of MLD group-specific queries

l           Whether to enable the function of dropping unknown IPv6 multicast data

2.5.2  Enabling MLD Snooping Querier

In an IPv6 multicast network running MLD, a Layer 3 multicast device acts as the MLD querier, responsible for sending MLD queries.

In a network that does not comprise Layer 3 multicast devices, however, it is a problem to implement an MLD querier, because Layer 2 device do not support MLD. To solve this problem, you can enable the MLD Snooping querier function on a Layer 2 device so that it can work as an MLD querier to create and maintain IPv6 multicast forwarding entries at the data link layer..

Follow these steps to enable the MLD Snooping querier:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Enable the MLD Snooping querier	mld-snooping querier	Required Disabled by default

 

 

2.5.3  Configuring MLD Timers

You can tune the MLD general query interval based on actual condition of the network.

Upon receiving an MLD query (general query or group-specific query), a host starts a timers for each IPv6 multicast group it has joined. This timer is initialized to a random value in the range of 0 to the maximum response time (the host obtains the value of the maximum response time from the Max Response Time field in the MLD query it received). When the timer value comes down to 0, the host sends an MLD report to the corresponding IPv6 multicast group.

An appropriate setting of the maximum response time for MLD queries allows hosts to respond to queries quickly and avoids burstiness of MLD traffic on the network caused by reports simultaneously sent by a large number of hosts when corresponding timers expires simultaneously.

l           For MLD general queries, you can configure the maximum response time to fill their Max Response time field.

l           For MLD group-specific queries, you can configure the MLD last-member query interval to fill their Max Response time field. Namely, for MLD group-specific queries, the maximum response time equals to the MLD last-member query interval.

I. Configuring MLD timers globally

Follow these steps to configure MLD timers globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter MLD Snooping view	mld-snooping	—
Configure the maximum response time for MLD general queries	max-response-time interval	Optional 10 seconds by default
Configure the MLD last-member query interval	last-member-query-interval interval	Optional 1 second by default

 

II. Configuring MLD timers in a VLAN

Follow these steps to configure MLD timers in a VLAN

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure MLD general query interval	mld-snooping query-interval interval	Optional 125 seconds by default
Configure the maximum response time for MLD general queries	mld-snooping max-response-time interval	Optional 10 seconds by default
Configure the MLD last-member query interval	mld-snooping last-member-query-interval interval	Optional 1 second by default

 

 

2.5.4  Configuring Source IPv6 Addresses of MLD Queries

Follow these steps to configure source IPv6 addresses of MLD queries:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure the source IPv6 address of MLD general queries	mld-snooping general-query source-ip { current-interface | ipv6-address }	Optional fe80::02ff:ffff:fe00:0001 by default
Configure the source IPv6 address of MLD group-specific queries	mld-snooping special-query source-ip { current-interface | ipv6-address }	Optional ffe80::02ff:ffff:fe00:0001 by default

 

 

2.5.5  Configuring the Function of Dropping Unknown IPv6 Multicast Data

Unknown IPv6 multicast data refers to IPv6 multicast data whose forwarding entries do not exist in the corresponding multicast forwarding table.

Follow these steps to configure the function of dropping unknown IPv6 multicast data in a VLAN:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Enable the function of dropping unknown IPv6 multicast data	mld-snooping drop-unknown	Required Disabled by default

 

 

2.6  Configuring an IPv6 Multicast Group Policy

2.6.1  Configuration Prerequisites

Before configuring an IPv6 multicast group filtering policy, complete the following tasks:

l           Enable MLD Snooping in the VLAN or enable MLD on the desired VLAN interface

Before configuring an IPv6 multicast group filtering policy, prepare the following data:

l           ACL rule for IPv6 multicast group filtering

l           Whether to enable IPv6 multicast source port filtering

l           The maximum number of IPv6 multicast groups that can pass the ports

l           Whether to enable IPv6 multicast group replacement

2.6.2  Configuring an IPv6 Multicast Group Filter

On a MLD Snooping–enabled switch, the configuration of an IPv6 multicast group filter allows the service provider to define limits of multicast programs available to different users.

In actual application, when a user requests a multicast program, the user’s host initiates an MLD report. After the message reaches the switch, the switch checks the report against the ACL rule configured on the receiving port. If this port can join this IPv6 multicast group, the switch adds this port to the MLD Snooping multicast group list; otherwise the switch drops this report message. Thus, the IPv6 multicast data will not be sent to this port. In this way, the service provider can control the VOD programs provided for multicast users.

I. Configuring an IPv6 multicast group filter globally

Follow these steps to configure an IPv6 multicast group globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter MLD Snooping view	mld-snooping	—
Configure an IPv6 multicast group filter	group-policy acl-number [ vlan vlan-list ]	Required No IPv6 filter configured by default

 

II. Configuring an IPv6 multicast group filter on a port or a group ports

Follow these steps to configure an IPv6 multicast group filer on a port or a group ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure an IPv6 multicast group filter		mld-snooping group-policy acl-number [ vlan vlan-list ]	Required No Ipv6 filter configured by default

 

2.6.3  Configuring IPv6 Multicast Source Port Filtering

With the IPv6 multicast source port filtering feature enabled, you can enable or disable a port as a multicast source port.

l           If this feature is enabled on a port, the port can be connected with IPv6 multicast receivers only rather than with multicast sources, because the port will block all IPv6 multicast data packets while it permits multicast protocol packets to pass.

l           If this feature is disabled on a port, the port can be connected with both multicast sources and IPv6 multicast receivers.

I. Configuring IPv6 multicast source port filtering globally

Follow these steps to configure IPv6 multicast source port filtering:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter MLD Snooping view	mld-snooping	—
Enable IPv6 multicast source port filtering	source-deny port interface-list	Required Disabled by default

 

II. Configuring IPv6 multicast source port filtering on a port or a group ports

Follow these steps to configure IPv6 multicast source port filtering on a port or a group ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Enable IPv6 multicast source port filtering		mld-snooping source-deny	Required Disabled by default

 

 

2.6.4  Configuring Maximum Multicast Groups that Can Pass Ports

By configuring the maximum number of IPv6 multicast groups that can pass a port or a group of ports, you can limit the number of number of multicast programs available to VOD users, thus to control the traffic on the port.

Follow these steps configure the maximum number of IPv6 multicast groups that can pass a port or a group of ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure the maximum number of IPv6 multicast groups that can pass the port(s)		mld-snooping group-limit limit [ vlan vlan-list ]	Optional 128 by default

 

 

2.6.5  Configuring IPv6 Multicast Group Replacement

For some special reasons, the number of IPv6 multicast groups passing through a switch or Ethernet port may exceed the number configured for the switch or the port. To address this situation, you can enable the IPv6 multicast group replacement function on the switch or certain Ethernet ports. When the number of IPv6 multicast groups an Ethernet port has joined exceeds the limit,

l           If the IPv6 multicast group replacement is enabled, the newly joined IPv6 multicast group automatically replaces an existing IPv6 multicast group with the lowest IPv6 address.

l           If the IPv6 multicast group replacement is not enabled, new MLD reports will be automatically discarded.

I. Configuring IPv6 multicast group replacement globally

Follow these steps to configure IPv6 multicast group replacement globally:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter MLD Snooping view	mld-snooping	—
Configure IPv6 multicast group replacement	overflow-replace [ vlan vlan-list ]	Required Disabled by default

 

II. Configuring IPv6 multicast group replacement on a port or a group ports

Follow these steps to configure IPv6 multicast group replacement on a port or a group ports:

To do...		Use the command...	Remarks
Enter system view		system-view	—
Enter the corresponding view	Enter Ethernet port view	interface interface-type interface-number	Use either command
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure IPv6 multicast group replacement		mld-snooping overflow-replace [ vlan vlan-list ]	Required Disabled by default

 

2.7  Displaying and Maintaining MLD Snooping

To do…	Use the command...	Remarks
View the information of IPv6 multicast groups learned by MLD Snooping	display mld-snooping group [ vlan vlan-id ] [ verbose ]	Available in any view
View the statistics information of MLD messages learned by MLD Snooping	display mld-snooping statistics	Available in any view
Clear MLD Snooping entries	reset mld-snooping group { ipv6-group-address | all } [ vlan vlan-id ]	Available in user view
Clear the statistics information of all kinds of MLD messages learned by MLD Snooping	reset mld-snooping statistics	Available in user view

 

 

2.8  MLD Snooping Configuration Examples

2.8.1  Simulated Host Joining

I. Network requirements

After the configuration, Host A and Host B, regardless of whether they have joined the IPv6 multicast group FF1E::1, can receive IPv6 multicast data addressed to the IPv6 multicast group FF1E::1. Figure 2-3 shows the network connections..

II. Network diagram

Figure 2-3 Network diagram for simulated hosts joining configuration

III. Configuration procedure

1)         Configuring a VLAN

# Create VLAN 100.

<SwitchA> system-view

[SwitchA] vlan 100

# Add ports GigabitEthernet1/0/1 through GigabitEthernet1/0/4 into VLAN 100.

[SwitchA-vlan100] port GigabitEthernet1/0/1 to GigabitEthernet1/0/4

[SwitchA-vlan100] quit

2)         Enabling simulated host joining to an IPv6 multicast group

# Enable MLD Snooping in VLAN 100.

[SwitchA] mld-snooping

[SwitchA-mld-snooping] quit

[SwitchA] vlan 100

[SwitchA-vlan100] mld-snooping enable

[SwitchA-vlan100] quit

# Enable the simulated host to join the IPv6 multicast group on GigabitEthernet1/0/3.

[SwitchA] interface GigabitEthernet1/0/3

[SwitchA- GigabitEthernet1/0/3] mld-snooping host-join ff1e::1 vlan 100

[SwitchA- GigabitEthernet1/0/3] quit

[SwitchA] interface GigabitEthernet1/0/4

[SwitchA- GigabitEthernet1/0/4] mld-snooping host-join ff1e::1 vlan 100

[SwitchA- GigabitEthernet1/0/4] quit

3)         Verifying the configuration

# View the detailed information of the IPv6 multicast group in VLAN 100.

[SwitchA] display mld-snooping group vlan 100 verbose

    Total 1 IP Group(s).

    Total 1 IP Source(s).

    Total 1 MAC Group(s).

 

  Port flags: D-Dynamic port, S-Static port, A-Aggregation port, C-Copy port

  Subvlan flags: R-Real VLAN, C-Copy VLAN

  Vlan(id):100.

    Total 1 IP Group(s).

    Total 1 IP Source(s).

    Total 1 MAC Group(s).

    Router port(s):total 1 port.

            GigabitEthernet1/0/1                                    (D) ( 00:01:30 )

    IP group(s):the following ip group(s) match to one mac group.

      IP group address:FF1E::1

        (::, FF1E::1):

          Attribute:    Host Port

          Host port(s):total 2 port.

            GigabitEthernet1/0/3                                    (D) ( 00:03:23 )

            GigabitEthernet1/0/4                                    (D) ( 00:03:23 )

    MAC group(s):

      MAC group address:3333-0000-0001

          Host port(s):total 2 port.

            GigabitEthernet1/0/3

            GigabitEthernet1/0/4

As shown above, GigabitEthernet1/0/3 and GigabitEthernet1/0/4 of Switch A have joined IPv6 multicast group (ff1e::1).

2.8.2  Static Router Port Configuration

I. Network requirements

No multicast protocol is running on Router B. After the configuration, Switch A should be able to forward IPv6 multicast data to Router B.Figure 2-4 shows the routernetwork connections.

II. Network diagram

Figure 2-4 Network diagram for static router port configuration

III. Configuration procedure

1)         Configuring a VLAN

# Create VLAN 100.

<SwitchA> system-view

[SwitchA] vlan 100

# Add ports GigabitEthernet1/0/1 through GigabitEthernet1/0/4 into VLAN 100.

[SwitchA-vlan100] port GigabitEthernet1/0/1 to GigabitEthernet1/0/4

[SwitchA-vlan100] quit

2)         Configuring a static router port

# Enable MLD Snooping in VLAN 100.

[SwitchA] mld-snooping

[SwitchA-mld-snooping] quit

[SwitchA] vlan 100

[SwitchA-vlan100] mld-snooping enable

[SwitchA-vlan100] quit

# Configure GigabitEthernet1/0/4 to be a static router port.

[SwitchA] interface GigabitEthernet1/0/4

[SwitchA- GigabitEthernet1/0/4] mld-snooping static-router-port vlan 100

[SwitchA- GigabitEthernet1/0/4] quit

3)         Verify the configuration

# View the detailed information of the IPv6 multicast group in VLAN 100.

[SwitchA] display mld-snooping group vlan 100 verbose

    Total 1 IP Group(s).

    Total 1 IP Source(s).

    Total 1 MAC Group(s).

 

  Port flags: D-Dynamic port, S-Static port, A-Aggregation port, C-Copy port

  Subvlan flags: R-Real VLAN, C-Copy VLAN

  Vlan(id):100.

    Total 1 IP Group(s).

    Total 1 IP Source(s).

    Total 1 MAC Group(s).

    Router port(s):total 2 port.

            GigabitEthernet1/0/1                                    (D) ( 00:01:30 )

            GigabitEthernet1/0/4                                    (S) ( 00:01:30 )

    IP group(s):the following ip group(s) match to one mac group.

      IP group address:FF1E::1

        (::, FF1E::1):

          Attribute:    Host Port

          Host port(s):total 1 port.

            GigabitEthernet1/0/3                                    (D) ( 00:03:23 )

    MAC group(s):

      MAC group address:3333-0000-0001

          Host port(s):total 1 port.

            GigabitEthernet1/0/3

As shown above, GigabitEthernet1/0/4 of Switch A has become a static router port.

2.9  Troubleshooting MLD Snooping

2.9.1  Switch Fails in Layer 2 Multicast Forwarding

I. Symptom

A switch fails to implement Layer 2 multicast forwarding.

II. Analysis

MLD Snooping is not enabled.

III. Solution

1)         Enter the display current-configuration command to view the running status of MLD Snooping.

2)         If MLD Snooping is not enabled, use the mld-snooping command to enable MLD Snooping globally and then use mld-snooping enable command to enable MLD Snooping in VLAN view.

3)         If MLD Snooping is disabled only for the corresponding VLAN, just use the mld-snooping enable command in VLAN view to enable MLD Snooping in the corresponding VLAN.

2.9.2  Configured IPv6 Multicast Group Policy Fails to Take Effect

I. Symptom

Although an IPv6 multicast group policy has been configured to allow hosts to join specific IPv6 multicast groups, the hosts can still receive IPv6 multicast data addressed to other groups.

II. Analysis

l           The IPv6 ACL rule is incorrectly configured

l           The IPv6 multicast group policy is not correctly applied

l           The function of dropping unknown IPv6 multicast data is not enabled, so unknown IPv6 multicast data is broadcast

l           Certain ports have been configured as static member ports of IPv6 multicasts groups, and this configuration conflicts with the configured IPv6 multicast group policy.

III. Solution

1)         Use the display acl ipv6 command to check the configured IPv6 ACL rule. Make sure that the IPv6 ACL rule conforms to the IPv6 multicast group policy to be implemented.

2)         Use the display this command to check whether the correct IPv6 multicast group policy has been applied. If not, use the mld-snooping group-policy command to apply the correct IPv6 multicast group policy.

3)         Use the display current-configuration command to whether the function of dropping unknown IPv6 multicast data is enabled. If not, use the drop-unknown or mld-snooping drop-unknown command to enable the function of dropping unknown IPv6 multicast data.

4)         Use the display mld-snooping group command to check whether any port has been configured as a static member port of any IPv6 multicast group. If so, check whether this configuration conflicts with the configured IPv6 multicast group policy. If any conflict exists, remove the port as a static member of the IPv6 multicast group.

 

Chapter 3  Multicast VLAN Configuration

3.1  Introduction to Multicast VLAN

As shown in Figure 3-1, in the traditional multicast programs-on-demand mode, when hosts that belong to different VLANs, Host A, Host B and Host C require multicast programs on demand service, Router A needs to forward a separate copy of the multicast data in each VLAN. This results in not only waste of network bandwidth but also extra burden on the Layer 3 device.

Figure 3-1 Before and after multicast VLAN is enabled on the Layer 2 device

To solve this problem, you can enable the multicast VLAN feature on Switch A, namely configure the VLANs to which these hosts belong as sub-VLANs of a multicast VLAN on the Layer 2 device and enable Layer 2 multicast in the multicast VLAN. After this configuration, Router A replicates the multicast data only within the multicast VLAN instead of forwarding a separate copy of the multicast data to each VLAN. This saves the network bandwidth and lessens the burden of the Layer 3 device.

3.2  Configuring Multicast VLAN

Follow these steps to configure a multicast VLAN:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Configure a specific VLAN as a multicast VLAN	multicast-vlan vlan-id enable	Required Disabled by default
Configure sub-VLANs for a specific multicast VLAN	multicast-vlan vlan-id subvlan vlan-list	Required No sub-VLAN by default.

 

 

 

3.3  Displaying and Maintaining Multicast VLAN

To do…	Use the command…	Remarks
Display information about a multicast VLAN and its sub-VLANs	display multicast-vlan [ vlan-id ]	Available in any view

 

3.4  Multicast VLAN Configuration Example

I. Network requirements

l           IGMP and PIM-DM are enabled on Router A’s GigabitEthernet1/0/1.

l           Switch A’s GigabitEthernet1/0/1 belongs to VLAN1024, GigabitEthernet1/0/2 through GigabitEthernet1/0/6 belong to VLAN11 through VLAN15 respectively, and Host A throgh Host E are connected to GigabitEthernet1/0/2 through GigabitEthernet1/0/6 of Switch A.

l           Configure the multicast VLAN feature so that Router A just sends multicast data to VLAN1024 rather than to each VLAN when the five hosts attached to Switch A need the multicast data.

II. Network diagram

Figure 3-2 Network diagram for multicast VLAN configuration

III. Configuration procedure

1)         Configuring Router A

# Enable IGMP and PIM-DM on GigabitEthernet 1/0/1.

<RouterA> system-view

[RouterA] multicast routing-enable

[RouterA] interface GigabitEthernet 1/0/1

[RouterA- GigabitEthernet 1/0/1] pim dm

[RouterA- GigabitEthernet 1/0/1] igmp enable

2)         Configuring Switch A

# Add GigabitEthernet 1/0/2 to VLAN11.

<SwitchA> system-view

[SwitchA] vlan 11

[SwitchA-vlan11] port GigabitEthernet 1/0/2

[SwitchA-vlan11] quit

The configuration for VLAN12 through VLAN15 is similar to the configuration for VLAN11.

# Configure VLAN1024 as multicast VLAN and configure VLAN11 through VLAN15 as its sub-VLANs.

[SwitchA] vlan 1024

[SwitchA-vlan1024] port GigabitEthernet 1/0/1

[SwitchA-vlan1024] quit

[SwitchA] multicast-vlan 1024 enable

[SwitchA] multicast-vlan 1024 subvlan 11 to 15

# Enable IGMP Snooping.

[SwitchA] igmp-snooping

[SwitchA-igmp-snooping] quit

[SwitchA] vlan 1024

[SwitchA-vlan1024] igmp-snooping enable

[SwitchA-vlan1024] quit

3)         Verify the configuration

# Display information about the multicast VLAN and its sub-VLANs.

[SwitchA] display multicast-vlan

 multicast vlan 1024's subvlan list:

   Vlan 11-15