Default Route Advertisement In BGP2 and BGP3 Version of The Border Gateway Protocol (RFC1397)
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2019-Feb-11
Internet Society Requests For Comment (RFCs)
This document speficies the recommendation of the BGP Working Group on default route advertisement support in BGP2  and BGP3  versions of the Border Gateway Protocol. [STANDARDS-TRACK]
Network Working Group D. Haskin Request for Comments: 1397 Bolt Beranek and Newman, Inc. January 1993
Default Route Advertisement In BGP2 And BGP3 Versions Of The Border Gateway Protocol
Status of this Memo
This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited.
This document specifies the recommendation of the BGP Working Group on default route advertisement support in BGP2  and BGP3  versions of the Border Gateway Protocol.
This recommendation only applies to BGP2 and BGP3 versions of the Border Gateway Protocol since starting with the BGP4  version a default route advertisement capability is built in the protocol.
The purpose of the default route advertisement capability is to advertise the IP address of a border gateway which can be used as the default next hop to destinations that are not listed explicitly in the BGP peer’s routing table.
This capability will allow routers, that are unable to maintain a complete routing table (e.g., due to its size) to learn a border gateway that is ready to handle the default traffic. Also, in contrast to static defaults, if there is more than one default gateway, this would make it possible for a BGP speaker to express a preference for one over the other. It also reduces the need to configure default routes in routers.
2. Default Route Advertisement
A default route is advertised in an UPDATE message that carries reachability information for network 0.0.0.0. A Network field of such an UPDATE message must contain the IP address 0.0.0.0 as the indication that it carries a default route. The NEXT_HOP path attribute of such a message provides the IP address of a border
Haskin [Page 1]
RFC 1397 Default Routes in Old BGPs January 1993
gateway that can be used as a default next hop to destinations that are not listed in the BGP peer’s routing table. The value o...