7. Deployment Considerations

BGP confederations have been widely deployed throughout the Internet for a number of years and are supported by multiple vendors.

Improper configuration of BGP confederations can cause routing information within an AS to be duplicated unnecessarily. This duplication of information will waste system resources, cause unnecessary route flaps, and delay convergence.

Care should be taken to manually filter duplicate advertisements caused by reachability information being relayed through multiple Member Autonomous Systems based upon the topology and redundancy requirements of the confederation.

Additionally, confederations (as well as route reflectors), by excluding different reachability information from consideration at different locations in a confederation, have been shown [RFC3345] to cause permanent oscillation between candidate routes when using the tie-breaking rules required by BGP [BGP-4]. Care must be taken when selecting MED values and tie-breaking policy to avoid these situations.

One potential way to avoid this is by configuring inter-Member-AS IGP metrics higher than intra-Member-AS IGP metrics and/or using other tie-breaking policies to avoid BGP route selection based on incomparable MEDs.