This requirement is not applicable for the DODIN Backbone. Review the router configuration to determine if it is compliant with this requirement. Step 1: Verify that an inbound route policy has been configured for each CE router as shown in the example below. router bgp xx address-family ipv4 unicast ! neighbor x.12.4.14 remote-as 64514 address-family ipv4 unicast route-policy FILTER_LONG_PREFIXES in ! ! neighbor x.12.4.16 remote-as 64516 address-family ipv4 unicast route-policy FILTER_LONG_PREFIXES in ! Step 2: Verify that the route policy permits only routes from each CE router with a prefix length of 24 or shorter or the least significant prefixes issued to the customer as shown in the example below. route-policy FILTER_LONG_PREFIXES if destination in PREFIX_LENGTH then pass else drop endif end-policy Note: The inbound route policy to filter customer prefixes can be nested with the above route policy as shown in the example below. route-policy CUST1_INBOUND_FILTER apply CUST1_FILTER apply FILTER_64514_ROUTES apply FILTER_LONG_PREFIXES end-policy Step 3: Review the prefix set referenced in the route policy above to determine if it only allows a prefix length 24 or shorter. prefix-set PREFIX_LENGTH 0.0.0.0/0 ge 8 le 24 end-set If the router is not configured to limit the prefix size on any inbound route advertisement to /24 or the least significant prefixes issued to the customer, this is a finding.