Allied Telesis Patch 89262-08 IGMP Snooping All-Group Entry, show ip igmp, Command Reference

Patch 89262-08 For AT-8900 Series Switches show ip igmp 23

IGMP Snooping All-Group Entry

Because IGMP is an IP-based protocol, multicast group membership for VLAN aware devices is on a per-VLAN basis. If at least one port in the VLAN is a member of a multicast group, multicast packets will be flooded onto all ports in the VLAN by default.

IGMP snooping enables the switch to forward multicast traffic intelligently on the switch. The switch listens to IGMP membership reports, queries and leaves messages to identify the switch ports that are members of multicast groups. Multicast traffic will only be forwarded to ports identified as members of the specific multicast group.

This enhancement allows network managers to prevent specified ports from acting as IGMP all-group ports, and specify which ports are allowed to behave as all-group entry ports, by using the ENABLE IP IGMP ALLGROUP command.

For example, consider a video streaming service which has 15 channels. When the switch receives IGMP membership reports destined for the address

239.0.0.2from an unauthorised user, all 15 channels of multicast data floods to that port, which may affect the service of the network. In order to avoid this, the network manager decides whether or not to allow a particular port to behave as an IGMP all-group port, e.g. port 8. Then, whenever the above IGMP membership report is sent, the switch will not automatically add port 8 as one of the egress ports for any IGMP membership report group, so video streaming will not get forwarded to disabled all-group ports selected by the network manager.

Command Reference

This enhancement modifies one command:

■SHOW IP IGMP

and has two new commands:

■ENABLE IP IGMP ALLGROUP

■DISABLE IP IGMP ALLGROUP

show ip igmp

Syntax SHOW IP IGMP [COUNTER] [INTERFACE=interface]

Description This command displays information about IGMP, and multicast group membership for each IP interface.

This enhancement includes the line “Disabled All-groups ports” on the output of this command, as shown in Figure 1 on page 24. Ports that are disabled have a “#” symbol next to the port number.

Patch 89262-08 for Software Release 2.6.2 C613-10402-00 REV H