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774 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
IGMP V3
25
PowerConnect(config)#ip igmp max-response-time 8
Syntax: [no] ip igmp max-response-time <num>
The <num> parameter specifies the IGMP maximum response time in number of seconds. Enter a
value from 1 through 10. The default is 10.
IGMP V3 and source specific multicast protocols
Enabling IGMP V3 enables source specific multicast (SSM) filtering for DVMRP and PIM Dense
(PIM-DM) for multicast group addresses in the 224.0.1.0 through 239.255.255.255 address
range. However, if PIM Sparse is used as the multicast protocol, the SSM protocol should be
enabled if you want to filter unwanted traffic before the Shortest Path Tree protocol switchover
occurs for groups in the 232/8 range. Not configuring the SSM protocol in PIM Sparse may cause
the switch or router to leak unwanted packets with the same group, but containing undesired
sources, to clients. After SPT switch over, the leak stops and source specific multicast works
correctly even without configuring the SSM protocol.
If the SSM protocol is not enabled and before the SPT switchover, the multicast router creates one
(*, G) entry for the entire multicast group, which can have many sources. If the SSM protocol is
enabled, one (S,G) entry is created for every member of the multicast group, even for members
with non-existent traffic. For example, if there are 1,000 members in the group, 1,000 (S,G) entries
will be created. Therefore, enabling the SSM protocol for PIM-SM requires more resources than
leaving the protocol disabled.
Enabling SSM
To enable the SSM protocol on a Dell PowerConnect device running PIM-SM, enter a command
such as the following.
PowerConnect(config)#router pim
PowerConnect(config-pim-router)#ssm-enable
Syntax: [no] ssm-enable
Enter the ssm-enable command under the router pim level to globally enable the SSM protocol on a
Layer 3 Switch.
Displaying IGMP V3 information on Layer 3 Switches
The sections below present the show commands available for IGMP V3 on Layer 3 Switches. For
show commands on Layer 2 Switches, use the show ip multicast commands which are discussed in
the section “IGMP snooping show commands” on page 853.
Displaying IGMP group status
NOTE
This report is available on Layer 3 Switches.
To display the status of all IGMP multicast groups on a device, enter the following command.