Lab 5 Introduction

The purpose of this lab is to build on lab #4 and gain more experience with routers and routing protocols. The particular focus of this lab is to expand the scope to include communication between administrative domains. In contrast to lab #4, in which all of the decisions on configuration, management and troubleshooting are confined to a single administrative entity (i.e., intra-domain routing and forwarding), this lab will consider the thorny issues related to enabling entire networks to interconnect, i.e., inter-domain routing and packet forwarding.

Unlike intra-domain routing, there is only one protocol that is used to establish forwarding tables between networks. That protocol is the Boarder Gateway Protocols (BGP). It can be argued that BGP is the protocol that is at the very heart of the Internet since the Internet is all about connecting networks. However, the fact that BGP is used to communicate routing information (in particular, information about which networks -- as indicated by IP address ranges -- are available) between administrative domains with potentially very different objectives means its requirements differ from standard intra-domain routing protocols. The primary requirements for BGP are that it established loop-free routes and that it be flexible (especially in terms of expressing policies). While the former is accomplished through the use of path vectors (similar in some respects to distance vector routing), the latter can lead to problems such as loss of connectivity, slow convergence and inefficient routes.

Students will be introduced to the basic concepts of inter-domain forwarding and routing in this lab by configuring and running tests a small network composed of IP routers. In this lab, each of the routers will act as a BGP speaker for an administrative domain (even though it will not be connected to a separate network). Expertise with inter-domain routing configuration is important if you are interested in eventually getting a job as a network administrator - especially with large Internet Service Providers whose networks connect to many other networks. The routers used in this lab are not emulated systems - they are Cisco routers running real instances of BGP such as would be observed in the Internet today. Students will gain further experience with the command line interface of Cisco's Internetwork Operating System (IOS).

This lab will be conducted entirely via Schooner. This lab will be about the same level of complexity as Lab #2 so please start early. Lab #5 will be the only lab in which inter-domain routing is covered, so if you would like to experiment with inter-domain routing in other ways, please see Prof. Barford for ideas.

Objectives