RFC 2283 (rfc2283) - Page 2 of 9
Multiprotocol Extensions for BGP-4
Alternative Format: Original Text Document
RFC 2283 Multiprotocol Extensions for BGP-4 February 1998
individual Network Layer protocols this document uses Address Family,
as defined in [RFC 1700].
One could further observe that the next hop information (the
information provided by the NEXT_HOP attribute) is meaningful (and
necessary) only in conjunction with the advertisements of reachable
destinations - in conjunction with the advertisements of unreachable
destinations (withdrawing routes from service) the next hop
information is meaningless. This suggests that the advertisement of
reachable destinations should be grouped with the advertisement of
the next hop to be used for these destinations, and that the
advertisement of reachable destinations should be segregated from the
advertisement of unreachable destinations.
To provide backward compatibility, as well as to simplify
introduction of the multiprotocol capabilities into BGP-4 this
document uses two new attributes, Multiprotocol Reachable NLRI
(MP_REACH_NLRI), and Multiprotocol Unreachable NLRI
(MP_UNREACH_NLRI). The first one (MP_REACH_NLRI) is used to carry the
set of reachable destinations together with the next hop information
to be used for forwarding to these destinations. The second one
(MP_UNREACH_NLRI) is used to carry the set of unreachable
destinations. Both of these attributes are optional and non-
transitive. This way a BGP speaker that doesn't support the
multiprotocol capabilities will just ignore the information carried
in these attributes, and will not pass it to other BGP speakers.
4. Multiprotocol Reachable NLRI - MP_REACH_NLRI (Type Code 14):
This is an optional non-transitive attribute that can be used for the
following purposes:
(a) to advertise a feasible route to a peer
(b) to permit a router to advertise the Network Layer address of
the router that should be used as the next hop to the destinations
listed in the Network Layer Reachability Information field of the
MP_NLRI attribute.
(c) to allow a given router to report some or all of the
Subnetwork Points of Attachment (SNPAs) that exist within the
local system
The attribute contains one or more triples
, where each triple is encoded as shown below: Bates, et. al. Standards Track