Cisco Routers for the Desperate, 2nd Edition

BGP Preparations

To run BGP, you must have the following:

• A router with at least 512MB of RAM

• Two ISPs, both willing to provide you with a BGP feed

• An IOS version that supports BGP version 4

• A block of IP addresses /24 or larger—several smaller chunks that add up to a /24 are useless for BGP

• An Autonomous System Number

• A routing registry entry for your network block

We'll look at each in turn.

Router Features

Let's dispose of the easy requirement first. Your router must have an IOS image that supports BGP. If your IOS doesn't support BGP, use your SmartNet contract to get a version that does.

Memory is a little more problematic. Each route announcement from a peer takes up a little bit of memory. When you are receiving full routes from two peers, your routing ...