Introduction

BGP End-of-RIB marker (EoR) is a BGP extension used to improve initial routing convergence between two BGP neighbors. It has application in initial convergence and BGP Graceful Restart.

BGP EoR Overview

• End-of-RIB has first been defined for BGP GR in RFC RFC4724. Later on, its functionality has been expended with the RFC draft draft-dong-idr-end-of-rib-use-extension-00 for general initial convergence outside of BGP GR.
• EoR is also defined in RT Route Constraint RFC4684
• The main problem it is trying to solve is when should the receive BGP neighbor start to calculate best path algorithm without changing it based on BGP Updates still not received. If one router has 5 BGP neighbors and receives least preferred route first, normally it would advertise it to its neighbors.
• For general support outside of BGP GR, BGP capability called End-of-RIB Capability is defined by the draft RFC.
• With such capability a BGP speaker advertises to its neighbor that it support receiving and sending EoR marker during the initial convergence. Once this capability is negotiated, but BGP speakers MUST use it.
• EoR Marker is an UPDATE message with no NLRI prefixes along with an empty withdraw NLRI. In normal situations empty UPDATE with empty NLRI and empty withdraw NLRI makes no sense.

Additional Resources

RFC4724 Graceful Restart Mechanism for BGP
RFC4684 Constrained Route Distribution for Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual Private Networks (VPNs)
BGP End-of-RIB Usage Extension and Negotiation

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