The Arista Multicast Source Discovery Protocol (MSDP) router must be configured to only accept MSDP packets from known MSDP peers.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-256047	SRG-NET-000364-RTR-000116	ARST-RT-000680	SV-256047r882483_rule	2025-02-20	2

Description
MSDP peering with customer network routers presents additional risks to the DISN Core, whether from a rogue or misconfigured MSDP-enabled router. To guard against an attack from malicious MSDP traffic, the receive path or interface filter for all MSDP-enabled RP routers must be configured to only accept MSDP packets from known MSDP peers.

ℹ️ Check
Review the Arista router configuration to determine if there is a receive path or interface filter to only accept MSDP packets from known MSDP peers. Step 1: Verify the MSDP peers and the corresponding interfaces. router msdp peer 10.11.12.2 ! peer 10.22.12.2 Step 2: Verify the access-list is configured inbound on MSDP peering interfaces. MSDP uses TCP port 639. Execute the command "sh ip access-list". ip access-list MSDP_FILTER 10 permit tcp host 10.1.12.2 host 10.11.17.9 eq 639 20 permit udp host 10.1.12.2 host 10.11.17.9 eq 500 30 permit udp 10.11.17.9 eq 500 host 10.1.12.2 40 deny ip any any log Step 3: Verify the ACL is applied on the interface. Execute the command "sh run int ethernet YY". interface ethernet 3 ip access-group MSDP_FILTER in If the Arista router is not configured to only accept MSDP packets from known MSDP peers, this is a finding.

ℹ️ Check

Review the Arista router configuration to determine if there is a receive path or interface filter to only accept MSDP packets from known MSDP peers. Step 1: Verify the MSDP peers and the corresponding interfaces. router msdp peer 10.11.12.2 ! peer 10.22.12.2 Step 2: Verify the access-list is configured inbound on MSDP peering interfaces. MSDP uses TCP port 639. Execute the command "sh ip access-list". ip access-list MSDP_FILTER 10 permit tcp host 10.1.12.2 host 10.11.17.9 eq 639 20 permit udp host 10.1.12.2 host 10.11.17.9 eq 500 30 permit udp 10.11.17.9 eq 500 host 10.1.12.2 40 deny ip any any log Step 3: Verify the ACL is applied on the interface. Execute the command "sh run int ethernet YY". interface ethernet 3 ip access-group MSDP_FILTER in If the Arista router is not configured to only accept MSDP packets from known MSDP peers, this is a finding.

✔️ Fix
Ensure the receive path or interface filter for all Arista MSDP routers only accepts MSDP packets from known MSDP peers. Step 1: Configure the MSDP peers. LEAF-1A(config)#router msdp LEAF-1A(config-router-msdp)# peer 10.11.12.2 LEAF-1A(config-router-msdp)# peer 10.22.12.2 Step 2: Configure the access-list inbound on MSDP peering interfaces. MSDP uses TCP port 639. LEAF-1A(config-router-msdp-peer-10.22.12.2)#ip access-list MSDP_FILTER LEAF-1A(config-acl-MSDP_FILTER)# 10 permit tcp host 10.1.12.2 host 10.11.17.9 eq 639 LEAF-1A(config-acl-MSDP_FILTER)# 20 permit udp host 10.1.12.2 host 10.11.17.9 eq 500 LEAF-1A(config-acl-MSDP_FILTER)# 30 permit udp 10.11.17.9 eq 500 host 10.1.12.2 LEAF-1A(config-acl-MSDP_FILTER)# 40 deny ip any any log Step 3: Apply the ACL on the interface. LEAF-1A(config-acl-MSDP_FILTER)#interface ethernet 3 LEAF-1A(config-if-Et3)# ip access-group MSDP_FILTER in

✔️ Fix

Ensure the receive path or interface filter for all Arista MSDP routers only accepts MSDP packets from known MSDP peers. Step 1: Configure the MSDP peers. LEAF-1A(config)#router msdp LEAF-1A(config-router-msdp)# peer 10.11.12.2 LEAF-1A(config-router-msdp)# peer 10.22.12.2 Step 2: Configure the access-list inbound on MSDP peering interfaces. MSDP uses TCP port 639. LEAF-1A(config-router-msdp-peer-10.22.12.2)#ip access-list MSDP_FILTER LEAF-1A(config-acl-MSDP_FILTER)# 10 permit tcp host 10.1.12.2 host 10.11.17.9 eq 639 LEAF-1A(config-acl-MSDP_FILTER)# 20 permit udp host 10.1.12.2 host 10.11.17.9 eq 500 LEAF-1A(config-acl-MSDP_FILTER)# 30 permit udp 10.11.17.9 eq 500 host 10.1.12.2 LEAF-1A(config-acl-MSDP_FILTER)# 40 deny ip any any log Step 3: Apply the ACL on the interface. LEAF-1A(config-acl-MSDP_FILTER)#interface ethernet 3 LEAF-1A(config-if-Et3)# ip access-group MSDP_FILTER in