← Back to Arista MLS EOS 4.X Router Security Technical Implementation Guide

V-256047

CAT II (Medium)

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

Rule ID

SV-256047r882483_rule

STIG

Arista MLS EOS 4.X Router Security Technical Implementation Guide

Version

V2R2

CCIs

CCI-002403

Discussion

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.

Check Content

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 Text

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