Review the router configuration to verify that it will reject routes belonging to the local AS. Step 1: verify that an inbound route policy has been configured for each external neighbor as shown in the example below. router bgp xx address-family ipv4 unicast ! neighbor x.1.23.3 remote-as yy keychain YYY_KEY_CHAIN ttl-security address-family ipv4 unicast route-policy BGP_FILTER_INBOUND in ! ! neighbor x.1.24.4 remote-as zz keychain ZZZ_KEY_CHAIN ttl-security address-family ipv4 unicast route-policy BGP_FILTER_INBOUND in ! ! Step 2: Review the route policy to determine if it is filtering at a minimum local prefixes as shown in the example below. route-policy BGP_FILTER_INBOUND if destination in LOCAL_PREFIX then drop else pass endif end-policy Note: If bogons are also filtered per previous requirement, the route policy would look similar to the following example: route-policy BGP_FILTER_INBOUND if destination in BOGON_PREFIXES then drop elseif destination in LOCAL_PREFIX then drop else pass endif end-policy Step 3: Review the prefix set referenced in the route policy above to determine if it includes the local global prefix as shown in the example below. prefix-set LOCAL_PREFIX x.13.1.0/24 le 32 end-set If the router is not configured to reject inbound route advertisements belonging to the local AS, this is a finding.