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CISC-RT-000920 - The Cisco Multicast Source Discovery Protocol (MSDP) switch must be configured to filter received source-active multicast advertisements for any undesirable multicast groups and sources.

Information

The interoperability of BGP extensions for interdomain multicast routing and MSDP enables seamless connectivity of multicast domains between autonomous systems. MP-BGP advertises the unicast prefixes of the multicast sources used by Protocol Independent Multicast (PIM) switches to perform RPF checks and build multicast distribution trees. MSDP is a mechanism used to connect multiple PIM sparse-mode domains, allowing RPs from different domains to share information about active sources. When RPs in peering multicast domains hear about active sources, they can pass on that information to their local receivers, thereby allowing multicast data to be forwarded between the domains. Configuring an import policy to block multicast advertisements for reserved, Martian, single-source multicast, and any other undesirable multicast groups, as well as any source-group (S, G) states with Bogon source addresses, would assist in avoiding unwanted multicast traffic from traversing the core.

Solution

Configure the MSDP switch to filter received source-active multicast advertisements for any undesirable multicast groups and sources as shown in the example below:

SW1(config)#ip access-list extended INBOUND_MSDP_SA_FILTER
SW1(config-ext-nacl)#deny ip any host 224.0.1.3 ! Rwhod
SW1(config-ext-nacl)#deny ip any host 224.0.1.24 ! Microsoft-ds
SW1(config-ext-nacl)#deny ip any host 224.0.1.22 ! SVRLOC
SW1(config-ext-nacl)#deny ip any host 224.0.1.2 ! SGI-Dogfight
SW1(config-ext-nacl)#deny ip any host 224.0.1.35 ! SVRLOC-DA
SW1(config-ext-nacl)#deny ip any host 224.0.1.60 ! hp-device-disc
SW1(config-ext-nacl)#deny ip any host 224.0.1.39 ! Auto-RP
SW1(config-ext-nacl)#deny ip any host 224.0.1.40 ! Auto-RP
SW1(config-ext-nacl)#deny ip any 232.0.0.0 0.255.255.255 ! SSM range
SW1(config-ext-nacl)#deny ip any 239.0.0.0 0.255.255.255 ! Admin scoped range
SW1(config-ext-nacl)#deny ip 10.0.0.0 0.255.255.255 any ! RFC 1918 address range
SW1(config-ext-nacl)#deny ip 127.0.0.0 0.255.255.255 any ! RFC 1918 address range
SW1(config-ext-nacl)#deny ip 172.16.0.0 0.15.255.255 any ! RFC 1918 address range
SW1(config-ext-nacl)#deny ip 192.168.0.0 0.0.255.255 any ! RFC 1918 address range
SW1(config-ext-nacl)#permit ip any any
SW1(config-ext-nacl)#exit
SW1(config)#ip msdp sa-filter in x.1.28.2 list INBOUND_MSDP_SA_FILTER

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XE_Switch_Y23M10_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-4, CAT|III, CCI|CCI-001368, Rule-ID|SV-221066r622190_rule, STIG-ID|CISC-RT-000920, STIG-Legacy|SV-110953, STIG-Legacy|V-101849, Vuln-ID|V-221066

Plugin: Cisco

Control ID: 4ccc740ce35834e66a4e063941bde18dabf89a7a1c7aaf86da019b4e4ac21694