Advertisement of the best external route in BGP

Document Type Replaced Internet-Draft (individual)
Last updated 2010-04-08 (latest revision 2009-03-26)
Replaced by draft-ietf-idr-best-external
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


The base BGP specifications prevent a BGP speaker from advertising any route that is not the best route for a BGP destination. This document specifies a modification of this rule. Routes are divided into two categories, "external" and "internal". A specification is provided for choosing a "best external route" (for a particular value of the Network Layer Reachability Information). A BGP speaker is then allowed to advertise its "best external route" to its internal BGP peers, even if that is not the best route for the destination. The document explains why advertising the best external route can improve convergence time without causing routing loops. Additional benefits include reduction of inter-domain churn and avoidance of permanent route oscillation. The document also generalizes the notions of "internal" and "external" so that they can be applied to Route Reflector Clusters and Autonomous System Confederations.


Pedro Marques (
Rex Fernando (
Enke Chen (
Prodosh Mohapatra (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)