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CISC-RT-000870 - The Cisco multicast Designated switch (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 multicast groups from sources that have been approved as shown in the example below:

SW2(config)#ip access-list extended IGMP_JOIN_FILTER
SW2(config-ext-nacl)#deny ip any 232.8.0.0 0.0.255.255
SW2(config-ext-nacl)#permit ip x.0.0.0 0.255.255.255 any
SW2(config-ext-nacl)#deny ip any any
SW2(config-ext-nacl)#exit

Step 2: Apply the filter to all host-facing Layer 3 and VLAN interfaces.

SW2(config)#int vlan3
SW2(config-if)#ip igmp access-group IGMP_JOIN_FILTER

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS_Switch_Y26M04_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-7(11), CAT|II, CCI|CCI-002403, Rule-ID|SV-220465r864161_rule, STIG-ID|CISC-RT-000870, STIG-Legacy|SV-111269, STIG-Legacy|V-102313, Vuln-ID|V-220465

Plugin: Cisco

Control ID: 73de66e860b1bed85a863d10f26f6f684e076fa6739598799c31d9586b8e7069