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CISC-RT-000860 - 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 only multicast groups 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 or MLD Membership Report messages to allow hosts to join only those multicast groups that have been approved.

Step 1: Configure the ACL to filter IGMP Membership Report messages as shown in the example.

RP/0/0/CPU0:R5(config)#ipv4 access-list IGMP_JOIN_FILTER
RP/0/0/CPU0:R5(config-ipv4-acl)#deny 239.8.0.0 0.0.255.255
RP/0/0/CPU0:R5(config-ipv4-acl)#exit

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|III, CCI|CCI-002403, Rule-ID|SV-216814r878125_rule, STIG-ID|CISC-RT-000860, STIG-Legacy|SV-105973, STIG-Legacy|V-96835, Vuln-ID|V-216814

Plugin: Cisco

Control ID: 7bf26c323ccd52260cd62811222e3bc77b4b95954337310b15514a9e81ca017f