Information
Accepting route advertisements belonging to the local AS can result in traffic looping or being black holed, or at a minimum using a non-optimized path.
NOTE: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.
Solution
Configure Arista eBGP routers to reject inbound route advertisements for prefixes that are not allocated to that specific customer.
Step 1: Configure the prefix-list to reject inbound route advertisements belonging to the local AS.
router(config)#ip prefix-list LOCAL_SCOPE_BOUNDARY
router(config-ip-pfx)#seq 10 deny 10.12.0.0/16
router(config-ip-pfx)#seq 100 permit 0.0.0.0/0 le32
Step 2: Configure a route-map to match the prefix-list.
router(config)#route-map LOCAL_AS deny
router(config-route-map-LOCAL_AS)#match IP address prefix-list LOCAL_SCOPE_BOUNDARY
router(config-route-map-LOCAL_AS)#exit
Step 3: Configure the route-map to be applied inbound to the appropriate BGP neighbor.
router(config)#router bgp 65000
router(config-router-bgp)#neighbor 10.12.0.0 prefix-list LOCAL_SCOPE_BOUNDARY in