This example shows the 'Standard Access-list' tool.  The access-list number defaults to 99 unless the 'List Number' field is defined and consists of 'deny' statements unless the 'ACL-Permits' option is selected.

Note: One or both of the 'Include-Self' and 'Customer-Recursive' options are necessary to generate any useful output.

It is unlikely that both line 2 & 3 would be pasted into the same router.  Line 2 would most likely be used on the router in AS5089, while line 3 would most likely be used on the router with a peering connection to AS5089.

Rank Filtering

For any given network, it's various peering relationships usually fall into one of the three categories: Transit, Free-Peering or Customer.

Transit relationships usually provide a path to every corner of the Internet, so if a customer network receives routes from one transit and forwards them to another transit this could result in major traffic flow between the transits across the customer network.

Free-Peering relationships usually provide a shortcut paths to between each other's own and customer networks only.  If a network received routes from  one free-peer and forwards them to another free-peer, the network could find itself being loaded with large chunks of it's neighboring networks traffic.

Customer relationships usually provide paths to the customers network and to any customers of the customer.  The routes received from one customer should be shared with other customers, free-peers and transits since that is what the customer relationship usually demands.  However, if a customer gives you routes received from another of it's transits, you could find yourself pushing large amount of your network traffic across his potentially small capacity.

When you configure your routing filters purely on the basis of what you can see through a network, you can find yourself suffering from mis-configurations which lead to the above.

In collecting the large amounts of raw routing information required by the various tools on this site, we have the means to calculate a connectivity index for each and every network on the Internet.  This allows to compare any two networks and assess which of the two is better connected to the rest of the Internet, and to make an calculated guess at the direction of each transit/customer relationship.  We can then use this to limit the customer recursion to those with worse connected networks.

When this 'Ranking-Filter' option is selected, all customer relationships are considered for expansion, even it they also appear to provide transit routing.  Without this option, all customer relationships are expanded except where they also provide transit routing.

If you haven't understood this explanation, we recommend that you set it the same as the 'Customer-Recursive' option.