V-273647

Discussion

Real-time multicast traffic can entail multiple large flows of data. Large unicast flows tend to be fairly isolated (i.e., someone doing a file download here or there), whereas multicast can have broader impact on bandwidth consumption, resulting in extreme network congestion. Hence, it is imperative that there is multicast admission control to restrict which multicast groups hosts are allowed to join via IGMP or MLD.

Check Content

Review the configuration of the DR to verify it is filtering IGMP or MLD report messages, allowing hosts to only join multicast groups from sources that have been approved.

Note: This requirement is only applicable to Source Specific Multicast (SSM) implementation. This requirement is not applicable to Any Source Multicast (ASM) since the filtering is being performed by the Rendezvous Pointerface router.

1. Verify all host facing interfaces are configured to filter IGMP Membership Report messages (IGMP joins) as shown in the example below:
ICX(conf)#interface ethernet 1/2/1
ICX(config-if-e10000-1/2/1)#ip igmp ver 3
ICX(config-if-e10000-1/2/1)#ip igmp access-group IGMP_JOIN_FILTER
ICX(config-ig-e1000-1/2/1)#show access-list all

2. Verify the output below (the access control list, or ACL) denies unauthorized groups or permits only authorized groups. The example below denies all groups from the 239.0.0.0/16 range.
Standard IP access list IGMP_JOIN_FILTER: 2 entries
10: deny 239.0.0.0 0.0.255.255
20: permit any

If the DR is not filtering IGMP or MLD report messages, this is a finding.