Read request and boundary subtypes
02The 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.
After re-advertisement completes, B sends A EoRR. The byte is2, not the Graceful Restart End-of-RIB marker.
Source for this drawing: RFC 7313 · Read RFC section 3.2 ↗
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A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
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These pictures are analogies to help you learn. The linked RFC explains the actual rules.
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Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
Subtype0 is the normal Route Refresh request, with or without the separate Outbound Route Filtering extension. Subtype1 is BoRR, Beginning of Route Refresh. Subtype2 is EoRR, End of Route Refresh.
- Subtype0 is the normal Route Refresh request, with or without the separate Outbound Route Filtering extension. Subtype1 is BoRR, Beginning of Route Refresh. Subtype2 is EoRR, End of Route Refresh.
- The fixed fields are AFI16bits, subtype8bits and SAFI8bits. For subtype1 or2, the length excluding the fixed BGP header must be4 octets. Do not apply that boundary-marker length rule to all subtype0 messages.
- Example family is AFI1/SAFI1 (IPv4 unicast). A boundary body is00 01 / subtype /01; the standard19-octet BGP header gives total length23. Fields are drawn to byte proportions, header omitted.
- Subtype255 is reserved; values other than0,1,2 are ignored under the enhanced error rules. Section6 records the original registry assignments, not a live registry snapshot.
RFC7313 §§3.2,4–6, RFC2918 §3. Only fixed four-octet examples are encoded here; this is not an ORF or general BGP parser.
Read the RFC section ↗