RFC 2966 (rfc2966) - Page 1 of 14
Domain-wide Prefix Distribution with Two-Level IS-IS
Alternative Format: Original Text Document
Network Working Group T. Li
Request for Comments: 2966 Procket Networks
Category: Informational T. Przygienda
Redback
H. Smit
Procket Networks
October 2000
Domain-wide Prefix Distribution with Two-Level IS-IS
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This document describes extensions to the Intermediate System to
Intermediate System (IS-IS) protocol to support optimal routing
within a two-level domain. The IS-IS protocol is specified in ISO
10589, with extensions for supporting IPv4 (Internet Protocol)
specified in RFC 1195 [2].
This document extends the semantics presented in RFC 1195 so that a
routing domain running with both level 1 and level 2 Intermediate
Systems (IS) [routers] can distribute IP prefixes between level 1 and
level 2 and vice versa. This distribution requires certain
restrictions to insure that persistent forwarding loops do not form.
The goal of this domain-wide prefix distribution is to increase the
granularity of the routing information within the domain.
1. Introduction
An IS-IS routing domain (a.k.a., an autonomous system running IS-IS)
can be partitioned into multiple level 1 (L1) areas, and a level 2
(L2) connected subset of the topology that interconnects all of the
L1 areas. Within each L1 area, all routers exchange link state
information. L2 routers also exchange L2 link state information to
compute routes between areas.
Informational