Build a network router on Linux

Zebra is open source TCP/IP routing software that is similar to Cisco's Internetworking Operating System (IOS). Flexible and powerful, it can handle routing protocols such as Routing Information Protocol (RIP), Open Shortest Path First (OSPF), Border Gateway Protocol (BGP), and all of their various flavors. This article shows how our authors set up Zebra and used it to manage routes dynamically in conjunction with real Cisco hardware.
Dynamic and robust routing is so essential to the workings of the Internet that any fledgling internetworking engineer must not only understand its concepts but also be able put it into practice in real situations. At the same time, this part of the routing scene is dominated by products from high-end network equipment providers such as Cisco, well outside the means of most individuals: learning would otherwise be limited to school or laboratory environments, with time and availability of the resources as perennial adversaries.

We were faced with such a dilemma when organizing a class on TCP/IP routing. Working with a small test network, we wanted to demonstrate various load-balancing scenarios with Routing Information Protocol (RIP) and Open Shortest Path First (OSPF). However, we were limited by the number of Cisco routers on hand. We did have some PCs available, so we began looking for alternative means to simulate Cisco routers using Linux.

Initially, we attempted to set up our test network using the traditional routed and gated daemons, but we quickly realized that their awkward configuration and limited capabilities created more hindrance than value. We decided to look for more modern means of completing our network and fortunately came upon Zebra.