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Default Route Advertisement In BGP2 and BGP3 Version of The Border Gateway Protocol (RFC1397)

IP.com Disclosure Number: IPCOM000002221D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 2 page(s) / 4K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D. Haskin: AUTHOR

Abstract

This document specifies the recommendation of the BGP Working Group on default route advertisement support in BGP2 [1] and BGP3 [2] versions of the Border Gateway Protocol.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 69% of the total text.

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.

Abstract

This document specifies the recommendation of the BGP Working Group

on default route advertisement support in BGP2 [1] and BGP3 [2]

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 [3] version a

default route advertisement capability is built in the protocol.

1. Overview

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

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 of the

ORIGIN attribute should be 2 (INCOMPLETE). The AS_PATH attribute

should be constructed according to the same rules that apply to a

conventional network advertisement.

If multiple default routes are advertised by a BGP speaker, the

INTER-AS-METRIC path attribute can be included in the corresponding

UPDATE messages to express preference levels for entry points to the

same AS.

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