RFC 7313 / START HERE
Enhanced BGP Route Refresh, before the details
BGP means Border Gateway Protocol, the protocol routers use to exchange reachability information. Enhanced Route Refresh adds boundaries to a repeated advertisement.
It lets one peer mark old received routes stale, replace them as fresh advertisements arrive, and remove any still stale when an explicit ending marker arrives. A Routing Information Base, or RIB, is stored routing information.
The idea in one picture
Begin inventory
Refresh entries
Remove stale
A simplified picture of the idea; the chapters explain the actual mechanisms.
Why it exists
A missed withdrawal can leave one router holding a route its neighbor no longer advertises. Beginning and ending markers help reconcile that received view without resetting the BGP session.
A familiar example
Imagine a network operator asking a neighboring router to repeat its current advertised routes. BoRR starts the inventory; EoRR ends it. The markers help correct stale state, but do not prove route ownership or promise unchanged forwarding.
Helpful background
You can start here without reading another RFC. If these ideas are unfamiliar, these short introductions may help.
What you’ll learn next
Begin with chapter one, or choose a topic.
- Advertise support for boundary markersBGP means Border Gateway Protocol. Peers exchange routing information; a Routing Information Base (RIB) stores it. Enhanced Route Refresh adds boundaries around a re-advertisement so a receiver can reconcile its saved routes.→
- Read request and boundary subtypesThe ROUTE-REFRESH message reuses the old reserved octet as a subtype. AFI (Address Family Identifier) and SAFI (Subsequent Address Family Identifier) identify the address family; the subtype says whether this is a request, a beginning marker or an ending marker.→
- Replace stale routes inside the boundariesAdj-RIB-Out is the set of routes a speaker advertises to a particular peer, subject to outbound policy. Beginning and ending markers let the receiver find a saved route whose withdrawal it missed.→
- Keep Graceful Restart EoR separateGraceful Restart has its own End-of-RIB marker, abbreviated EoR. Enhanced Route Refresh uses EoRR. Their names are similar, but their meanings and ordering rules differ.→
- Handle unknown and malformed markersEnhanced error handling applies when capability70 was received. Unknown subtypes and malformed known boundary markers have different required outcomes.→
- Bound waiting without inventing securityIf the ending marker never arrives, an implementation may choose a local stale-retention limit. That operational choice does not make route information authentic.→
This introduction explains RFC 7313 (2014). Read the original RFC ↗