Introduction - Huawei Quidway NetEngine80E Configuration Manual

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing

7.1 Introduction

By building IS-IS networks, you can enable IS-IS to discover and calculate routes in ASs.
7.1.1 Basic Concepts of IS-IS
As an IGP, IS-IS is used inside an AS. IS-IS is a link-state protocol. It uses the SPF algorithm
to calculate routes.
The Intermediate System-to-Intermediate System (IS-IS) is a dynamic routing protocol that was
originally created by the International Organization for Standardization (ISO) for its
Connectionless Network Protocol (CLNP).
To support the IP routing, the Internet Engineering Task Force (IETF) extended and modified
IS-IS in RFC 1195. IS-IS can therefore be applied to both TCP/IP and OSI environments. This
type of IS-IS is called the Integrated IS-IS or Dual IS-IS.
As an Interior Gateway Protocol (IGP), IS-IS is used in Autonomous Systems (ASs). IS-IS is a
link-state protocol. It uses the Shortest Path First (SPF) algorithm to calculate routes. It resembles
the Open Shortest Path First (OSPF) protocol.
IS-IS Areas
To support large-scale networks, the IS-IS adopts a two-level structure in a Routing Domain
(RD). A large RD is divided into one or more areas. The intra-area routes are managed by the
Level-1 routers, whereas the inter-area routes are managed by the Level-2 routers.
Figure 7-1
Area 1 is a backbone area. All routers in this area are Level-2 routers. The other four areas are
non-backbone areas. They are connected to Area 1 through Level-1-2 routers.
Figure 7-1 IS-IS topology
Issue 02 (2014-09-30)
shows an IS-IS network. Its topology is similar to that of a multi-area OSPF network.
Area2
L1
L1/2
L2
Area4
L1/2
L1
L1
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Area3
L1/2
L2 Area1
L2
L2
Area5
L1/2
L1
7 IS-IS Configuration
L1
L1

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