The Arista Multicast Source Discovery Protocol (MSDP) router must be configured to filter source-active multicast advertisements to external MSDP peers to avoid global visibility of local-only multicast sources and groups.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
low	V-255994	SRG-NET-000018-RTR-000008	ARST-RT-000080	SV-255994r882324_rule	2025-02-20	2

Description
To avoid global visibility of local information, there are a number of source-group (S, G) states in a PIM-SM domain that must not be leaked to another domain, such as multicast sources with private address, administratively scoped multicast addresses, and the auto-RP groups (224.0.1.39 and 224.0.1.40). Allowing a multicast distribution tree, local to the core, to extend beyond its boundary could enable local multicast traffic to leak into other autonomous systems and customer networks.

Description

To avoid global visibility of local information, there are a number of source-group (S, G) states in a PIM-SM domain that must not be leaked to another domain, such as multicast sources with private address, administratively scoped multicast addresses, and the auto-RP groups (224.0.1.39 and 224.0.1.40). Allowing a multicast distribution tree, local to the core, to extend beyond its boundary could enable local multicast traffic to leak into other autonomous systems and customer networks.

ℹ️ Check
Review the Arista router configuration to determine if there is export policy to block local source-active multicast advertisements. Step 1: Verify that an outbound source-active filter is bound to each MSDP peer. To verify the MSDP peer is configured and to verify the source-active filter is configured outbound, execute the command "show ip msdp peer X.1.12.2 and show ip msdp summary". router msdp peer 10.1.12.2 sa-filter out PIM_NEIGHBOR_SA_FILTER Step 2: Review the access lists referenced by the source-active filters and verify that MSDP source-active messages being sent to MSDP peers do not leak advertisements that are local. To verify IP access lists are configured, execute the command "show ip access-lists". ip access-list PIM_NEIGHBOR_SA_FILTER 10 deny ip any 224.1.1.0/24 20 deny ip any 224.1.2.0/24 30 deny ip any 224.1.3.0/24 40 deny ip any 224.1.4.0/24 100 permit ip any any If the router is not configured with an export policy to block local source-active multicast advertisements, this is a finding.

ℹ️ Check

Review the Arista router configuration to determine if there is export policy to block local source-active multicast advertisements. Step 1: Verify that an outbound source-active filter is bound to each MSDP peer. To verify the MSDP peer is configured and to verify the source-active filter is configured outbound, execute the command "show ip msdp peer X.1.12.2 and show ip msdp summary". router msdp peer 10.1.12.2 sa-filter out PIM_NEIGHBOR_SA_FILTER Step 2: Review the access lists referenced by the source-active filters and verify that MSDP source-active messages being sent to MSDP peers do not leak advertisements that are local. To verify IP access lists are configured, execute the command "show ip access-lists". ip access-list PIM_NEIGHBOR_SA_FILTER 10 deny ip any 224.1.1.0/24 20 deny ip any 224.1.2.0/24 30 deny ip any 224.1.3.0/24 40 deny ip any 224.1.4.0/24 100 permit ip any any If the router is not configured with an export policy to block local source-active multicast advertisements, this is a finding.

✔️ Fix
Step 1: Configure Arista router to ensure an export policy is implemented on all MSDP routers to avoid global visibility of local multicast (S,G) states. router msdp peer 10.1.12.2 sa-filter in PIM_NEIGHBOR_SA_FILTER Step 2: Configure the source active access-list. ip access-list PIM_NEIGHBOR_SA_FILTER 10 deny ip any 224.1.1.0/24 20 deny ip any 224.1.2.0/24 30 deny ip any 224.1.3.0/24 40 deny ip any 224.1.4.0/24 100 permit ip any any

✔️ Fix

Step 1: Configure Arista router to ensure an export policy is implemented on all MSDP routers to avoid global visibility of local multicast (S,G) states. router msdp peer 10.1.12.2 sa-filter in PIM_NEIGHBOR_SA_FILTER Step 2: Configure the source active access-list. ip access-list PIM_NEIGHBOR_SA_FILTER 10 deny ip any 224.1.1.0/24 20 deny ip any 224.1.2.0/24 30 deny ip any 224.1.3.0/24 40 deny ip any 224.1.4.0/24 100 permit ip any any