Internet Group Management Protocol (IGMP) establishes and maintains the multicast group memberships between a Layer 3 multicast device and the hosts on the directly connected subnet.

IGMP has the following versions:

· IGMPv1 (defined by RFC 1112).

· IGMPv2 (defined by RFC 2236).

· IGMPv3 (defined by RFC 3376).

All IGMP versions support the ASM model. IGMPv3 can directly implement the SSM model. IGMPv1 and IGMPv2 must work with the IGMP SSM mapping feature to implement the SSM model. For more information about the ASM and SSM models, see "Multicast overview."

IGMPv1 overview

IGMPv1 manages multicast group memberships based on the query and response mechanism.

All routers that run IGMP on the same subnet can get IGMP membership report messages (often called reports) from hosts. However, only one router can act as the IGMP querier to send IGMP query messages (often called queries). The querier election mechanism determines which router acts as the IGMP querier on the subnet.

In IGMPv1, the DR elected by the multicast routing protocol (such as PIM) acts as the IGMP querier. For more information about DR, see "Configuring PIM."

Figure 1 IGMP queries and reports

As shown in Figure 1, Host B and Host C are interested in the multicast data addressed to the multicast group G1. Host A is interested in the multicast data addressed to G2. The following process describes how the hosts join the multicast groups and how the IGMP querier (Router B in Figure 1) maintains the multicast group memberships:

1. The hosts send unsolicited IGMP reports to the multicast groups they want to join without having to wait for the IGMP queries from the IGMP querier.

2. The IGMP querier periodically multicasts IGMP queries (with the destination address of 224.0.0.1) to all hosts and routers on the local subnet.

After receiving a query message, the host whose delay timer expires first sends an IGMP report to the multicast group G1 to announce its membership for G1. In this example, Host B sends the report message. Host C suppresses its own report for G1 after receiving the report from Host B. Because IGMP routers already know that G1 has at least one member, other members do not need to report their memberships. This host IGMP report suppression mechanism helps reduce traffic on the local subnet.

3. At the same time, Host A sends a report to the multicast group G2 after receiving a query.

4. Through the query and response process, the IGMP routers (Router A and Router B) determine that the local subnet has members of G1 and G2. The multicast routing protocol (PIM, for example) on the routers generates (*, G1) and (*, G2) multicast forwarding entries, where asterisk (*) represents any multicast source. These entries are the basis for subsequent multicast forwarding.

5. When the multicast data addressed to G1 or G2 reaches an IGMP router, the router looks up the multicast forwarding table. Based on the (*, G1) or (*, G2) entries, the router forwards the multicast data to the local subnet. Then, the receivers on the subnet can receive the data.

IGMPv1 does not define a leave group message (often called a leave message). When an IGMPv1 host is leaving a multicast group, it stops sending reports to that multicast group. If the subnet has no members for a multicast group, the IGMP routers will not receive any report addressed to that multicast group. In this case, the routers clear the information for that multicast group after a period of time.

IGMPv2 enhancements

Backwards-compatible with IGMPv1, IGMPv2 has introduced a querier election mechanism and a leave-group mechanism.

Querier election mechanism

In IGMPv1, the DR elected by the Layer 3 multicast routing protocol (such as PIM) acts as the querier.

IGMPv2 introduced an independent querier election mechanism. The querier election process is as follows:

1. Initially, every IGMPv2 router assumes itself to be the querier. Each router sends IGMP general query messages (often called general queries) to all hosts and routers on the local subnet. The destination address of general queries is 224.0.0.1.

2. After receiving a general query, every IGMPv2 router compares the source IP address of the query message with its own interface address. The router with the lowest IP address becomes the querier. All the other IGMPv2 routers become non-queriers.

3. All the non-queriers start the other querier present timer. If a router receives an IGMP query from the querier before the timer expires, it resets this timer. Otherwise, the router considers that the querier has timed out. In this case, the router initiates a new querier election process.

"Leave group" mechanism

In IGMPv1, when a host leaves a multicast group, it does not send any notification to the multicast routers. The multicast routers determine whether a group has members by using the maximum response time. This adds to the leave latency.

In IGMPv2, when a host is leaving a multicast group, the following process occurs:

1. The host sends a leave message to all routers on the local subnet. The destination address of leave messages is 224.0.0.2.

2. After receiving the leave message, the querier sends a configurable number of IGMP group-specific queries to the group that the host is leaving. Both the destination address field and the group address field of the message are the address of the multicast group that is being queried.

3. One of the remaining members (if any on the subnet) in the group should send a report within the maximum response time advertised in the group-specific queries.

4. If the querier receives a report for the group before the maximum response timer expires, it maintains the memberships for the group. Otherwise, the querier assumes that the local subnet has no member hosts for the group and stops maintaining the memberships for the group.

IGMPv3 enhancements

IGMPv3 is based on and is compatible with IGMPv1 and IGMPv2. It enhances the control capabilities of hosts and the query and report capabilities of IGMP routers.

Enhancements in control capability of hosts

IGMPv3 introduced two source filtering modes (Include and Exclude). These modes allow a host to join a designated multicast group and to choose whether to receive or reject multicast data from the specified multicast sources. When a host joins a multicast group, one of the following occurs:

· If the host expects to receive multicast data from specific sources like S1, S2, …, it sends a report with the Filter-Mode denoted as "Include Sources (S1, S2, …)."

· If the host expects to reject multicast data from specific sources like S1, S2, …, it sends a report with the Filter-Mode denoted as "Exclude Sources (S1, S2, …)."

As shown in Figure 2, the network has two multicast sources: Source 1 (S1) and Source 2 (S2). Both of these sources can send multicast data to the multicast group G. Host B wants to receive the multicast data addressed to G from Source 1 but not from Source 2.

Figure 2 Flow paths of source-and-group-specific multicast traffic

In IGMPv1 or IGMPv2, Host B cannot select multicast sources when it joins the multicast group G. The multicast streams from both Source 1 and Source 2 flow to Host B whether or not it needs them.

In IGMPv3, Host B can explicitly express that it needs to receive the multicast data that Source 1 sends to the multicast group G (denoted as (S1, G)). It also can explicitly express that it does not want to receive the multicast data that Source 2 sends to multicast group G (denoted as (S2, G)). As a result, Host B receives only multicast data from Source 1.

Enhancements in query and report capabilities

IGMPv3 introduces IGMP group-and-source queries and IGMP reports carrying group records.

· Query message carrying the source addresses

IGMPv3 is compatible with IGMPv1 and IGMPv2 and supports IGMP general queries and IGMP group-specific queries. It also introduces IGMP group-and-source-specific queries.

¡ A general query does not carry a group address or a source address.

¡ A group-specific query carries a group address, but no source address.

¡ A group-and-source-specific query carries a group address and one or more source addresses.

· Reports containing multiple group records

Unlike an IGMPv1 or IGMPv2 report, an IGMPv3 report is destined to 224.0.0.22 and contains one or more group records. Each group record contains a multicast group address and a multicast source address list.

Group records include the following categories:

¡ IS_IN—The current filtering mode is Include. The report sender requests the multicast data only from the sources specified in the Source Address field.

¡ IS_EX—The current filtering mode is Exclude. The report sender requests the multicast data from any sources except those specified in the Source Address field.

¡ TO_IN—The filtering mode has changed from Exclude to Include.

¡ TO_EX—The filtering mode has changed from Include to Exclude.

¡ ALLOW—The Source Address field contains a list of additional sources from which the receiver wants to obtain data. If the current filtering mode is Include, these sources are added to the multicast source list. If the current filtering mode is Exclude, these sources are deleted from the multicast source list.

¡ BLOCK—The Source Address field contains a list of the sources from which the receiver no longer wants to obtain data. If the current filtering mode is Include, these sources are deleted from the multicast source list. If the current filtering mode is Exclude, these sources are added to the multicast source list.

IGMP SSM mapping

An IGMPv3 host can explicitly specify multicast sources in its IGMPv3 reports. From the reports, the IGMP router can obtain the multicast source addresses and directly provide the SSM service. However, an IGMPv1 or IGMPv2 host cannot specify multicast sources in its IGMPv1 or IGMPv2 reports.

The IGMP SSM mapping feature enables the IGMP router to provide SSM support for IGMPv1 or IGMPv2 receiver hosts. The router translates (*, G) in IGMPv1 or IGMPv2 reports into (G, INCLUDE, (S1, S2...)) based on the configured IGMP SSM mappings.

The IGMP SSM mapping feature does not process IGMPv3 reports.

Figure 3 IGMP SSM mapping

As shown in Figure 3, on an SSM network, Host A, Host B, and Host C run IGMPv1, IGMPv2, and IGMPv3, respectively. To provide the SSM service for Host A and Host B, you must configure the IGMP SSM mapping feature on Router A.

After IGMP SSM mappings are configured, Router A checks the multicast group address G in the received IGMPv1 or IGMPv2 report, and performs the following operations:

· If G is not in the SSM group range, Router A provides the ASM service.

· If G is in the SSM group range but does not match any IGMP SSM mappings, Router A drops the message.

· If G is in the SSM group range and matches IGMP SSM mappings, Router A translates (*, G) in the report into (G, INCLUDE, (S1, S2...)) to provide SSM services.

For more information about SSM group ranges, see "Configuring PIM."

IGMP support for VPNs

IGMP maintains group memberships on a per-interface base. After receiving an IGMP message on an interface, IGMP processes the packet within the VPN to which the interface belongs. IGMP only communicates with other multicast protocols within the same VPN instance.

Protocols and standards

· RFC 1112, Host Extensions for IP Multicasting

· RFC 2236, Internet Group Management Protocol, Version 2

· RFC 3376, Internet Group Management Protocol, Version 3

IGMP configuration task list

Tasks at a glance
Configuring basic IGMP features: · (Required.) Enabling IGMP · (Optional.) Specifying an IGMP version · (Optional.) Configuring a static group member · (Optional.) Configuring a multicast group policy
Adjusting IGMP performance: (Optional.) Configuring IGMP query and response parameters (Optional.) Enabling fast-leave processing
(Optional.) Enabling IGMP NSR
(Optional.) Configuring IGMP SSM mappings

Configuring basic IGMP features

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

· Configure any unicast routing protocol so that all devices can interoperate at the network layer.

· Configure PIM.

· Determine the IGMP version.

· Determine the multicast group and multicast source addresses for static group member configuration.

· Determine the ACL to be used by the multicast group policy.

Enabling IGMP

Enable IGMP on the interface where the multicast group memberships are established and maintained.

To enable IGMP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable IP multicast routing and enter MRIB view.	multicast routing [ vpn-instance vpn-instance-name ]	By default, IP multicast is disabled.
3. Return to system view.	quit	N/A
4. Enter interface view.	interface interface-type interface-number	N/A
5. Enable IGMP.	igmp enable	By default, IGMP is disabled.

Specifying an IGMP version

For IGMP to operate correctly, you must specify the same IGMP version for all routers on the same subnet.

To specify an IGMP version:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Specify an IGMP version.	igmp version version-number	The default setting is 2.

Configuring a static group member

You can configure an interface as a static group member of a multicast group. The interface can always receive multicast data addressed to the specified multicast group.

A static group member does not respond to IGMP queries. When you complete or cancel this configuration on an interface, the interface does not send an unsolicited IGMP report or leave message. This is because the interface is not a real member host of the multicast group.

Configuration restrictions and guidelines

The interface to be configured as a static group member has the following restrictions:

· If the interface is IGMP and PIM-SM enabled, it must be a PIM-SM DR.

· If the interface is IGMP enabled but not PIM-SM enabled, it must be an IGMP querier.

For more information about PIM-SM and DR, see "Configuring PIM."

Configuration procedure

To configure a static group member:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure the interface as a static group member.	igmp static-group group-address [ source source-address ]	By default, an interface is not a static group member of any multicast groups.

Configuring a multicast group policy

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

To configure a multicast group policy:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure a multicast group policy.	igmp group-policy acl-number [ version-number ]	By default, an interface is not configured with a multicast group policy. Hosts attached to the interface can join any multicast groups.

NOTE:

This configuration cannot control a static group member.

Adjusting IGMP performance

Before adjusting IGMP performance, complete the following tasks:

· Configure any unicast routing protocol so that all devices can interoperate at the network layer.

· Configure basic IGMP features.

Configuring IGMP query and response parameters

The following are IGMP query and response parameters:

· IGMP querier's robustness variable—Number of times for retransmitting IGMP queries in case of packet loss. A higher robustness variable makes the IGMP querier more robust, but it increases the timeout time for multicast groups.

· IGMP startup query interval—Interval at which an IGMP querier sends IGMP general queries at startup.

· IGMP startup query count—Number of IGMP general queries that an IGMP querier sends at startup.

· IGMP general query interval—Interval at which an IGMP querier sends IGMP general queries to check for multicast group members on the network.

· IGMP last member query interval—In IGMPv2, it sets the interval at which a querier sends group-specific queries after receiving a leave message. In IGMPv3, it sets the interval at which a querier sends group-and-source-specific queries after receiving a report that changes multicast source and group mappings.

· IGMP last member query count—In IGMPv2, it sets the number of group-specific queries that a querier sends after receiving a leave message. In IGMPv3, it sets the number of group-and-source-specific queries that a querier sends after receiving a report that changes multicast source and group mappings.

· IGMP maximum response time—Maximum time before a receiver responds with a report to an IGMP general query. This per-group timer is initialized to a random value in the range of 0 to the maximum response time specified in the IGMP query. When the timer value for a group decreases to 0, the receiver sends an IGMP report to the group.

· IGMP other querier present timer—Lifetime for an IGMP querier after a non-querier receives an IGMP general query. If the non-querier does not receive a new query from the querier when this timer expires, the non-querier considers that the querier has failed and starts a new querier election.

Configuration restrictions and guidelines

When you configure the IGMP query and response parameters, follow these guidelines:

· You can configure the IGMP query and response parameters either for the current port in interface view or globally for all ports in IGMP view. The configuration made in interface view takes priority over the configuration made in IGMP view.

· To avoid frequent IGMP querier changes, set the IGMP other querier present timer greater than the IGMP general query interval. In addition, configure the same IGMP other querier present timer for all IGMP routers on the same subnet.

· To avoid mistakenly deleting multicast receivers, set the IGMP general query interval greater than the maximum response time for IGMP general queries.

· To speed up the response to IGMP queries and avoid simultaneous timer expirations that cause IGMP report traffic bursts, set an appropriate maximum response time.

¡ For IGMP general queries, the maximum response time is set by the max-response-time command.

¡ For IGMP group-specific queries and IGMP group-and-source-specific queries, the maximum response time equals the IGMP last member query interval.

· The following configurations take effect only on the devices that run IGMPv2 and IGMPv3:

¡ Maximum response time for IGMP general queries.

¡ IGMP last member query interval.

¡ IGMP last member query count.

¡ IGMP other querier present interval.

Configuring the IGMP query and response parameters globally

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP view.	igmp [ vpn-instance vpn-instance-name ]	N/A
3. Set the IGMP querier's robustness variable.	robust-count count	By default, the IGMP querier's robustness variable is 2.
4. Set the IGMP startup query interval.	startup-query-interval interval	By default, the IGMP startup query interval equals one quarter of the IGMP general query interval.
5. Set the IGMP startup query count.	startup-query-count count	By default, the IGMP startup query count equals the IGMP querier's robustness variable.
6. Set the IGMP general query interval.	query-interval interval	By default, the IGMP general query interval is 125 seconds.
7. Set the IGMP last member query interval.	last-member-query-interval interval	By default, the IGMP last member query interval is 1 second.
8. Set the IGMP last member query count.	last-member-query-count count	By default, the IGMP last member query count equals the IGMP querier's robustness variable.
9. Set the maximum response time for IGMP general queries.	max-response-time time	By default, the maximum response time for IGMP general queries is 10 seconds.
10. Set the IGMP other querier present timer.	other-querier-present-interval interval	By default, the IGMP other querier present timer is [ IGMP general query interval ] × [ IGMP robustness variable ] + [ maximum response time for IGMP general queries ] / 2.

Configuring the IGMP query and response parameters on an interface

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Set the IGMP querier's robustness variable.	igmp robust-count count	By default, the IGMP querier's robustness variable is 2.
4. Set the IGMP startup query interval.	igmp startup-query-interval interval	By default, the IGMP startup query interval equals one quarter of the IGMP general query interval.
5. Set the IGMP startup query count.	igmp startup-query-count count	By default, the IGMP startup query count equals the IGMP querier's robustness variable.
6. Set the IGMP general query interval.	igmp query-interval interval	By default, the IGMP general query interval is 125 seconds.
7. Set the IGMP last member query interval.	igmp last-member-query-interval interval	By default, the IGMP last member query interval is 1 second.
8. Set the IGMP last member query count.	igmp last-member-query-count count	By default, the IGMP last member query count equals the IGMP querier's robustness variable.
9. Set the maximum response time for IGMP general queries.	igmp max-response-time time	By default, the maximum response time for IGMP general queries is 10 seconds.
10. Set the IGMP other querier present timer.	igmp other-querier-present-interval interval	By default, the IGMP other querier present timer is [ IGMP general query interval ] × [ IGMP robustness variable ] + [ maximum response time for IGMP general queries ] / 2.

Enabling fast-leave processing

This feature enables an IGMP querier to send a leave notification directly to the upstream without sending group-specific queries or group-and-source-specific queries after receiving a leave message. This reduces leave latency and preserves the network bandwidth.

The fast-leave processing configuration takes effect only when the switch runs IGMPv2 or IGMPv3.

To enable fast-leave processing:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Enable fast-leave processing.	igmp fast-leave [ group-policy acl-number ]	By default, fast-leave processing is disabled.

Enabling IGMP NSR

This feature enables the switch to back up information about IGMP interfaces and IGMP forwarding entries to the standby process. After an active/standby switchover, the switch can recover the information without cooperation of other devices. This prevents the active/standby switchover from affecting the multicast service.

To enable IGMP NSR:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable IGMP NSR.	igmp non-stop-routing	By default, IGMP NSR is disabled.

Configuring IGMP SSM mappings

This feature enables the switch to provide SSM services for IGMPv1 or IGMPv2 hosts.

This feature does not process IGMPv3 messages. As a best practice, enable IGMPv3 on the receiver-side interface to ensure that IGMPv3 reports can be processed.

Configuration prerequisites

Before you configure IGMP SSM mappings, complete the following tasks:

· Configure any unicast routing protocol so that all devices in the domain can interoperate at the network layer.

· Configure basic IGMP features.

Configuration procedure

To configure an IGMP SSM mapping:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IGMP view.	igmp [ vpn-instance vpn-instance-name ]	N/A
3. Configure an IGMP SSM mapping.	ssm-mapping source-address acl-number	By default, IGMP SSM mappings are not configured.

Displaying and maintaining IGMP

CAUTION:

The reset igmp group command might cause multicast data transmission failures.

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

Task	Command
Display IGMP information about multicast groups.	display igmp [ vpn-instance vpn-instance-name ] group [ group-address \| interface interface-type interface-number ] [ static \| verbose ]
Display IGMP information for interfaces.	display igmp[ vpn-instance vpn-instance-name ] interface [ interface-type interface-number ] [ host] [ verbose ]
Display IGMP SSM mappings.	display igmp [ vpn-instance vpn-instance-name ] ssm-mapping group-address
Clear dynamic IGMP group entries.	reset igmp [ vpn-instance vpn-instance-name ] group { all \| interface interface-type interface-number { all \| group-address [ mask { mask \| mask-length } ] [ source-address [ mask { mask \| mask-length } ] ] } }

IGMP configuration examples

Basic IGMP features configuration examples

Network requirements

As shown in Figure 4:

· OSPF and PIM-DM run on the network.

· VOD streams are sent to receiver hosts in multicast. Receiver hosts of different organizations form stub networks N1 and N2. Host A and Host C are receiver hosts in N1 and N2, respectively.

· IGMPv2 runs between Switch A and N1, and between the other two switches and N2. Switch A acts as the IGMP querier in N1. Switch B acts as the IGMP querier in N2 because it has a lower IP address.

Configure the routers to meet the following requirements:

· The hosts in N1 can join only multicast group 224.1.1.1.

· The hosts in N2 can join any multicast groups.

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 OSPF on the switches in the PIM-DM domain. (Details not shown.)

3. Enable IP multicast routing, IGMP, and PIM-DM:

# On Switch A, enable IP multicast routing.

<SwitchA> system-view

[SwitchA] multicast routing

[SwitchA-mrib] quit

# Enable IGMP on VLAN-interface 100.

[SwitchA] interface vlan-interface 100

[SwitchA-Vlan-interface100] igmp enable

[SwitchA-Vlan-interface100] quit

# Enable PIM-DM on VLAN-interface 101.

[SwitchA] interface vlan-interface 101

[SwitchA-Vlan-interface101] pim dm

[SwitchA-Vlan-interface101] quit

# On Switch B, enable IP multicast routing.

<SwitchB> system-view

[SwitchB] multicast routing

[SwitchB-mrib] quit

# Enable IGMP on VLAN-interface 200.

[SwitchB] interface vlan-interface 200

[SwitchB-Vlan-interface200] igmp enable

[SwitchB-Vlan-interface200] quit

# Enable PIM-DM on VLAN-interface 201.

[SwitchB] interface vlan-interface 201

[SwitchB-Vlan-interface201] pim dm

[SwitchB-Vlan-interface201] quit

# On Switch C, enable IP multicast routing.

<SwitchC> system-view

[SwitchC] multicast routing

[SwitchC-mrib] quit

# Enable IGMP on VLAN-interface 200.

[SwitchC] interface vlan-interface 200

[SwitchC-Vlan-interface200] igmp enable

[SwitchC-Vlan-interface200] quit

# Enable PIM-DM on VLAN-interface 202.

[SwitchC] interface vlan-interface 202

[SwitchC-Vlan-interface202] pim dm

[SwitchC-Vlan-interface202] quit

4. Configure a multicast group policy on Switch A so that the hosts connected to VLAN-interface 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] interface vlan-interface 100

[SwitchA-Vlan-interface100] igmp group-policy 2001

[SwitchA-Vlan-interface100] quit

Verifying the configuration

# Display IGMP information on VLAN-interface 200 of Switch B.

[SwitchB] display igmp interface vlan-interface 200

Vlan-interface200(10.110.2.1):

IGMP is enabled.

IGMP version: 2

Query interval for IGMP: 125s

Other querier present time for IGMP: 255s

Maximum query response time for IGMP: 10s

Querier for IGMP: 10.110.2.1 (This router)

IGMP groups reported in total: 1

IGMP SSM mapping configuration example

Network requirements

As shown in Figure 5:

· OSPF runs on the network.

· The PIM-SM domain uses both the ASM model and SSM model for multicast delivery. VLAN-interface 104 on Switch D acts as the C-BSR and C-RP. The SSM group range is 232.1.1.0/24.

· IGMPv3 runs on VLAN-interface 400 of Switch D. The receiver host runs IGMPv2, and does not support IGMPv3. Therefore, the receiver host cannot specify expected multicast sources in its membership reports.

· Source 1, Source 2, and Source 3 send multicast packets to multicast groups in the SSM group range.

Configure the IGMP SSM mapping feature on Switch D so that the receiver host can receive multicast data from Source 1 and Source 3 only.

Figure 5 Network diagram

Table 1 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
Source 1	—	133.133.1.1/24	Source 3	—	133.133.3.1/24
Source 2	—	133.133.2.1/24	Receiver	—	133.133.4.1/24
Switch A	Vlan-int100	133.133.1.2/24	Switch C	Vlan-int300	133.133.3.2/24
Switch A	Vlan-int101	192.168.1.1/24	Switch C	Vlan-int103	192.168.3.1/24
Switch A	Vlan-int104	192.168.4.2/24	Switch C	Vlan-int102	192.168.2.2/24
Switch B	Vlan-int200	133.133.2.2/24	Switch D	Vlan-int400	133.133.4.2/24
Switch B	Vlan-int101	192.168.1.2/24	Switch D	Vlan-int103	192.168.3.2/24
Switch B	Vlan-int102	192.168.2.1/24	Switch D	Vlan-int104	192.168.4.1/24

Configuration procedure

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

2. Configure OSPF on the switches in the PIM-SM domain. (Details not shown.)

3. Enable IP multicast routing, PIM-SM, and IGMP:

# On Switch D, enable IP multicast routing.

<SwitchD> system-view

[SwitchD] multicast routing

[SwitchD-mrib] quit

# Enable IGMPv3 on the receiver-side interface (VLAN-interface 400).

[SwitchD] interface vlan-interface 400

[SwitchD-Vlan-interface400] igmp enable

[SwitchD-Vlan-interface400] igmp version 3

[SwitchD-Vlan-interface400] quit

# Enable PIM-SM on the other interfaces.

[SwitchD] interface vlan-interface 103

[SwitchD-Vlan-interface103] pim sm

[SwitchD-Vlan-interface103] quit

[SwitchD] interface vlan-interface 104

[SwitchD-Vlan-interface104] pim sm

[SwitchD-Vlan-interface104] quit

# On Switch A, enable IP multicast routing, and enable PIM-SM on each interface.

<SwitchA> system-view

[SwitchA] multicast routing

[SwitchA-mrib] quit

[SwitchA] interface vlan-interface 100

[SwitchA-Vlan-interface100] pim sm

[SwitchA-Vlan-interface100] quit

[SwitchA] interface vlan-interface 101

[SwitchA-Vlan-interface101] pim sm

[SwitchA-Vlan-interface101] quit

[SwitchA] interface vlan-interface 104

[SwitchA-Vlan-interface104] pim sm

[SwitchA-Vlan-interface104] quit

# Configure Switch B and Switch C in the same way Switch A is configured. (Details not shown.)

4. Configure a C-BSR and a C-RP on Switch D.

[SwitchD] pim

[SwitchD-pim] c-bsr 192.168.4.1

[SwitchD-pim] c-rp 192.168.4.1

[SwitchD-pim] quit

5. Configure the SSM group range:

# Configure the SSM group range as 232.1.1.0/24 on Switch D.

[SwitchD] acl number 2000

[SwitchD-acl-basic-2000] rule permit source 232.1.1.0 0.0.0.255

[SwitchD-acl-basic-2000] quit

[SwitchD] pim

[SwitchD-pim] ssm-policy 2000

[SwitchD-pim] quit

# Configure the SSM group range on Switch A, Switch B, and Switch C in the same way Switch D is configured. (Details not shown.)

6. Configure IGMP SSM mappings on Switch D.

[SwitchD] igmp

[SwitchD-igmp] ssm-mapping 133.133.1.1 2000

[SwitchD-igmp] ssm-mapping 133.133.3.1 2000

[SwitchD-igmp] quit

Verifying the configuration

# Display IGMP SSM mappings for multicast group 232.1.1.1 on Switch D.

[SwitchD] display igmp ssm-mapping 232.1.1.1

Group: 232.1.1.1

Source list:

133.133.1.1

133.133.3.1

# Display information about IGMP multicast groups that hosts have dynamically joined on Switch D.

[SwitchD] display igmp group

IGMP groups in total: 1

Vlan-interface400(133.133.4.2):

IGMP groups reported in total: 1

Group address Last reporter Uptime Expires

232.1.1.1 133.133.4.1 00:02:04 off

# Display the PIM routing table on Switch D.

[SwitchD] display pim routing-table

Total 0 (*, G) entry; 2 (S, G) entry

(133.133.1.1, 232.1.1.1)

RP: 192.168.4.1

Protocol: pim-ssm, Flag:

UpTime: 00:13:25

Upstream interface: Vlan-interface104

Upstream neighbor: 192.168.4.2

RPF prime neighbor: 192.168.4.2

Downstream interface(s) information:

Total number of downstreams: 1

1: Vlan-interface400

Protocol: igmp, UpTime: 00:13:25, Expires: -

(133.133.3.1, 232.1.1.1)

RP: 192.168.4.1

Protocol: pim-ssm, Flag:

UpTime: 00:13:25

Upstream interface: Vlan-interface103

Upstream neighbor: 192.168.3.1

RPF prime neighbor: 192.168.3.1

Downstream interface(s) information:

Total number of downstreams: 1

1: Vlan-interface400

Protocol: igmp, UpTime: 00:13:25, Expires: -

Troubleshooting IGMP

No membership information on the receiver-side router

Symptom

When a host sends a report for joining the multicast group G, no membership information of the multicast group G exists on the router closest to that host.

Solution

To resolve the problem:

1. Use the display igmp interface command to verify that the networking, interface connection, and IP address configuration are correct.

2. Use the display current-configuration command to verify that multicast routing is enabled. If it is not enabled, use the multicast routing command in system view to enable IP multicast routing. In addition, verify that IGMP is enabled on the associated interfaces.

3. Use the display igmp interface command to verify that the IGMP version on the interface is lower than that on the host.

4. Use the display current-configuration interface command to verify that no ACL rule has been configured to filter out the reports sent by the host to the multicast group G.

5. If the problem persists, contact H3C Support.

Inconsistent membership information on the routers on the same subnet

Symptom

Different memberships are maintained on different IGMP routers on the same subnet.

Solution

To resolve the problem:

1. Use the display current-configuration command to verify the IGMP information on the interfaces.

2. Use the display igmp interface command on all routers on the same subnet to verify the IGMP-related timer settings. Make sure the settings are consistent on all the routers.

3. Use the display igmp interface command to verify that all the routers on the same subnet are running the same IGMP version.

4. If the problem persists, contact H3C Support.

07-IP Multicast Configuration Guide

Overview

IGMPv1 overview

IGMPv2 enhancements

Querier election mechanism

"Leave group" mechanism

IGMPv3 enhancements

Enhancements in control capability of hosts

Enhancements in query and report capabilities

IGMP support for VPNs

IGMP configuration task list

Configuring basic IGMP features

Enabling IGMP

Configuring a static group member

Configuration restrictions and guidelines

Configuration procedure

Configuring a multicast group policy

Configuring IGMP query and response parameters

Configuration restrictions and guidelines

Configuring the IGMP query and response parameters globally

Configuring the IGMP query and response parameters on an interface

Enabling fast-leave processing

Displaying and maintaining IGMP

IGMP configuration examples

Network requirements

Configuration procedure

Verifying the configuration

Network requirements

Configuration procedure

Verifying the configuration

Troubleshooting IGMP

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Solution

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