In Depth Guide to IS-IS Routing E-Book

Mamta Devi

• Herausgeber: BookRix
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2023

Beschreibung

Unlock the Power of IS-IS Routing: Your Comprehensive Guide to Intermediate System to Intermediate System Routing Master the intricacies of IS-IS routing with our comprehensive eBook! Whether you're a networking professional looking to enhance your knowledge or a beginner eager to dive into the world of Intermediate System to Intermediate System routing, this guide is your go-to resource. Inside, you'll discover: - Clear explanations of IS-IS fundamentals, from protocol basics to advanced configurations. - Step-by-step tutorials and real-world examples for hands-on learning. - In-depth insights into IS-IS network design, security, and best practices. - Expert tips for troubleshooting and optimizing your IS-IS network. - A comparison of IS-IS with other routing protocols, helping you make informed decisions.With our eBook in your toolkit, you'll have the knowledge and skills to design, implement, and manage robust IS-IS routing networks. Take your networking expertise to the next level and ensure the success of your IT projects. Get started today!

Leseprobe

Mamta Devi

In Depth Guide to IS-IS Routing

Learn Intermediate System to Intermediate System Routing from scratch

BookRix GmbH & Co. KG81371 Munich

Table of Content

 Introduction to Intermediate System to Intermediate SystemIntegrated IS-IS Configuration on Cisco IOSAuthentication process in IS-ISPseudonode and IS-IS DISIS-IS MetricRedistribution in IS-ISSummarization in IS-ISFiltering in IS-ISRoute Leaking in IS-IS

This eBook is based on IS-IS Routing Protocol that has been collected from different sources and people. For more information about this ebook. Kindly write to [email protected]. I will happy to help you.

Copyright 2023 by Mamta Devi

This eBook is a guide and serves as a first guide. This book has been written on the advice of many experts and sources who have good command over Routing protocols and networking. They are listed at the end of this book.All images used in this book are taken from the LAB which is created by experts. All rights reserved, including the right to reproduce this book or portions thereof in any form whatsoever. For any query reach out to the author through email.

Introduction to Intermediate System to Intermediate System

IS-IS, or Intermediate System to Intermediate System, is an interior gateway protocol used for routing in computer networks. Similar to OSPF (Open Shortest Path First), IS-IS is a link-state routing protocol that facilitates the exchange of routing information. It establishes neighbor adjacencies, defines routing areas, exchanges link-state packets, builds a link-state database, and utilizes the Dijkstra SPF (Shortest Path First) algorithm to determine the optimal path to each destination, which is subsequently installed in the routing table.

In its early days, IS-IS was developed by DEC (Digital Equipment Corporation) for the CLNS (Connectionless-mode Network Service) and CLNP (Connectionless-mode Network Protocol) protocols, both of which were alternatives to IP. Unlike today, where IP is the predominant protocol, IS-IS was originally designed to work with these ISO (International Organization for Standardization) protocols.

The terminology used in IS-IS differs from that of OSPF:

Router in IS-IS is referred to as "Intermediate System."

Host is termed as "End System."

IS-IS was initially created for CLNS, not IP. This is why it is called IS-IS, where IS stands for "Intermediate System." However, over time, IS-IS was adapted to route IP as well, and this variant is known as "integrated IS-IS."

Even though IP is now ubiquitous, IS-IS still retains references to CLNP/CLNS in certain contexts. For instance, when configuring a router ID, known as a Network Entity Title (NET), it must be set up in the NSAP (Network Service Access Point Address) format, similar to an IP address but not automatically configured.

Another notable aspect of IS-IS is its encapsulation. Unlike other routing protocols such as OSPF and EIGRP, which encapsulate data in IP packets, IS-IS operates directly over Ethernet headers, employing its unique header format.

IS-IS is widely used in large service provider network backbones due to its scalability. In this overview, we will explore the key aspects of IS-IS and how it operates.

Areas and Router Roles

IS-IS employs a different approach to areas compared to OSPF. In IS-IS, an entire router belongs to an area, as opposed to only a subset of its interfaces as in OSPF. IS-IS does not feature a distinct backbone area; instead, the backbone is formed by a sequence of routers. There are three types of routers in IS-IS:

Level 1 system: These are intra-area routers that only possess knowledge of their local area and learn prefixes exclusively from their own area. They create a level 1 link-state database and SPF tree for the area.

Level 2 system: Level 2 routers, also known as backbone routers, are aware of both intra-area and inter-area routes. They create a level 2 link-state database and SPF tree for the backbone.

Level 1-2 system: Level 1-2 routers have dual roles, functioning as both level 1 and level 2 routers. Consequently, they create separate level 1 and level 2 link-state databases, each with its own SPF tree. This configuration is the default setting on Cisco IOS routers. Just like other routing protocols, IS-IS routers send hello packets to establish neighbor adjacencies. Routers will only form neighbor adjacencies with those at the same level. Here are some examples to illustrate the concept:

Single Area:

In a single area scenario, level 1 routers will form level 1 neighbor adjacencies.

Two Areas: When two areas are involved, level 1 routers within an area can only reach external destinations through level 2 routers. Each area has a level 1-2 router to facilitate this communication.

Multiple Areas: In a more complex topology with multiple areas, routers are connected with various neighbor adjacencies. Level 2 routers create a continuous backbone.