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RFC 2918 / START HERE

BGP Route Refresh, before the details

BGP Route Refresh

BGP means Border Gateway Protocol. Route Refresh lets one established peer ask another to send its selected routing advertisements again, so local policy can re-examine them. A route advertisement describes destinations and a path; it is not an actual data packet.

Start the guide See the 6 chapters ↓

The idea in one picture

  1. Request one family

  2. Re-advertise selected routes

  3. Re-examine under policy

A simplified picture of the idea; the chapters explain the actual mechanisms.

Why it exists

An inbound routing-policy change can need routes a speaker previously rejected and did not retain. RFC2918 adds a family-specific request without resetting the session. This September2000 Proposed Standard is updated by RFC7313, which adds explicit begin/end markers and related handling.

A familiar example

Imagine asking a colleague to resend the relevant page of an approved list after your selection rules change. The colleague still follows its own sharing rules, and you still apply yours. This analogy does not imply all routes are trusted or installed; the chapters show actual message bytes, request direction and the later marker rules.

Helpful background

You can start here without reading another RFC. If these ideas are unfamiliar, these short introductions may help.

BGPRFC 4271 · beginner overview ↗BGP capability advertisementRFC 5492 · beginner overview ↗CIDRRFC 4632 · beginner overview ↗

What you’ll learn next

Begin with chapter one, or choose a topic.

  1. Re-examine routes without resetting the sessionA local inbound-policy change can need fresh advertisements from an established peer.
  2. Check which peer advertised receive supportReceive capability, request direction and family scope are separate checks.
  3. Read the actual ROUTE-REFRESH messageA Type 5 message carries a family, rather than another capability TLV.
  4. Replay only the relevant outbound advertisementsA refresh preserves family scope and each side’s policy boundaries.
  5. Use the later begin and end markers deliberatelyRFC7313 adds explicit boundaries and peer/family-scoped stale-route cleanup.
  6. Stop invalid or out-of-order enhanced messagesThe enhanced update distinguishes ignore, notification and restart-order guards.
Start with chapter one →

This introduction explains RFC 2918 (2000). Read the original RFC ↗