BGP – Prevent becoming a Transit-AS

1. AS-Path Filtering
2. No-export Community
3. Prefix-list Filtering
4. Distribute List Filtering

AS-Path Filtering

ip as-path access-list 1 permit ^$
neighbor x.x.x.x filter-list 1 out

No-export Community

ip bgp-community new-format
route-map NO-EXPORT
  ​set community no-export
neighbor x.x.x.x route-map NO-EXPORT in
neighbor x.x.x.x send-community

Prefix-list Filtering

ip prefix-list NO-TRANSIT permit x.x.x.x/x
neighbor x.x.x.x prefix-list NO-TRANSIT out

Distribute List Filtering

access-list x deny x.x.x.x y.y.y.y
neighbor x.x.x.x distribute-list x out

Links

• https://networkdirection.net/articles/routingandswitching/bgppreventtransitas/
• https://ccie4all.wordpress.com/2013/03/03/bgp-transit-as/