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CISC-RT-000870 - The Cisco multicast Designated Router (DR) must be configured to filter the Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Report messages to allow hosts to join a multicast group only from sources that have been approved by the organization.

Information

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.

Solution

Configure the DR to filter the IGMP and MLD report messages to allow hosts to join only those multicast groups from sources that have been approved as shown in the example.

Step 1: Configure the access list to filter multicast joins as shown in the example below.

RP/0/0/CPU0:R2(config)#ipv4 access-list IGMP_JOIN_FILTER
RP/0/0/CPU0:R2(config-ipv4-acl)#deny ip any 232.8.0.0 0.0.255.255
RP/0/0/CPU0:R2(config-ipv4-acl)#permit ip x.0.0.0 0.255.255.255 any
RP/0/0/CPU0:R2(config-ipv4-acl)#deny ip any any

Step 2: Apply the filter to all host facing interfaces.

RP/0/0/CPU0:R5(config)#router igmp
RP/0/0/CPU0:R5(config-igmp)#interface g0/0/1/0
RP/0/0/CPU0:R5(config-igmp-default-if)#access-group IGMP_JOIN_FILTER
RP/0/0/CPU0:R5(config-igmp-default-if)#exit
RP/0/0/CPU0:R5(config-igmp)#interface g0/0/1/1
RP/0/0/CPU0:R5(config-igmp-default-if)#end

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XR_Router_Y26M01_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-7(11), CAT|II, CCI|CCI-002403, Rule-ID|SV-216815r878126_rule, STIG-ID|CISC-RT-000870, STIG-Legacy|SV-105975, STIG-Legacy|V-96837, Vuln-ID|V-216815

Plugin: Cisco

Control ID: 940308670ccb58f72fa401761374374f85e3979ea55ac4c25cce56c85883d00f