Configuring IGMP Snooping

Summary: Networking › Switching › Edge › Synapse

Overview of IGMP Snooping

IGMP Snooping is a short term for Internet Group Management Protocol Snooping, a mechanism running on a layer 2 device for managing and controlling multicast groups. A Layer 2 device running IGMP Snooping analyzes the received IGMP packets, establishes a mapping relationship between ports and MAC multicast addresses, and forwards multicast data according to the mapping relationship. When the Layer 2 device does not run IGMP Snooping, the multicast data is broadcast at Layer 2; when the Layer 2 device runs IGMP Snooping, the multicast data of the known multicast group will not be broadcast at Layer 2, but at Layer 2. As shown in the figure below, when the Layer 2 multicast device does not run IGMP Snooping, the IP multicast packets are broadcast in the VLAN; when the Layer 2 multicast device runs IGMP Snooping, the IP multicast packets are only sent to the group members recipient.

Configuring

• Enabling IGMP Snooping

SWITCH( config)# igmp snooping

SWITCH( config)# no igmp snooping

Enable/disable IGMP Snooping function; disabled by default. Global configuration mode.

SWITCH( config-if)# igmp snooping mrouter interface IFNAME

SWITCH( config-if)# no igmp snooping mrouter interface IFNAME

Configure/delete IGMP Snooping upstream port; optional configuration. SVI interface mode.

SWITCH( config-if)# igmp snooping static-group IPADDR source IPADDR interface IFNAME

SWITCH( config-if)# no igmp snooping static-group IPADDR source IPADDR interface IFNAME

Configure/delete IGMP Snooping static group; optional configuration. SVI interface mode.

SWITCH( config-if)# igmp snooping fast-leave

SWITCH( config-if)# no igmp snooping fast-leave

Configure/delete IGMP Snooping fast leave function; optional configuration. SVI interface mode.

Examples

Simplified topology: Basic configuration /roles: (top down) server: During the test, VLC is used as the multicast server to provide the multicast service: udp://225.0.0.1:1234, the server IP is 3.3.3.10 router: Run the multicast routing protocol and enable IGMP, and use Ruijie S57 Layer 3 switch to simulate the test. The main configurations are as follows:

Enable multicast routing

ip multicast-routing Configure the uplink port , connect to the server, here is simply to select the PIM dense mode, the actual network scale is large, and the multicast use is less, it is recommended to use the sparse mode interface GigabitEthernet 0/23 no switchport no ip proxy- arp ip pim dense-mode ip address 3.3.3.3 255.255.255.0 Configure the downlink port. The PIM dense mode is simply selected here. The actual network scale is large and the multicast usage is small. It is recommended to use the sparse mode interface VLAN 1 no ip proxy- arp ip pim dense-mode ip address 2.2.2.1 255.255.255.0

SWITCH:

Multicast can be enabled

igmp snooping Client: Watch server multicast video through udp://225.0.0.1:1234, IP 2.2.2.10

Display Information

• View IGMP Snooping Multicast Groups

SWITCH#show igmp snooping groups

SWITCH#show igmp snooping interface {ifname}

Example:

IGMP Snooping information for vlan1 IGMP Snooping enabled

Snooping Querier none

IGMP Snooping other querier timeout is 255 seconds Group Membership interval is 260 seconds IGMPv2 fast-leave is disabled IGMPv1/v2 Report suppression enabled IGMPv3 Report suppression enabled

Router port detection using IGMP Queries

Number of router-ports: 2 Number of Groups: 2 Number of Joins: 891 Number of Leaves: 4 Active Ports: gigabitEthernet0/1 gigabitEthernet0/2

• Viewing IGMP Snooping Routing Port Information

SWITCH#show igmp snooping mrouter vlan1

Example:

SWITCH#show igmp snooping mrouter vlan1

VLAN Interface IP-address Expires 1 gigabitEthernet0/18(dynamic) 2.2.2.1 00:03:34 gigabitEthernet0/20(static) — —

SWITCH#show igmp snooping statistics interface vlan1

IGMP Snooping statistics for vlan1 Group Count : 2 IGMP reports received : 893 IGMP leaves received : 4 IGMPv1 query warnings : 0 IGMPv2 query warnings : 456 IGMPv3 query warnings : 0