The main purpose of this post is to show how prefix lists work and how to decipher them vs regular access lists. Access-lists do a great job on Cisco devices, not just for security but all kinds of route filtering, QoS, and so on. A prefix list is a bit different form an access-list, and it’s important to know the differences and when to use either. I’ve created the following simple topology to illustrate what I’m going to be doing. There are 2 routers, both running BGP. Router1 will have numerous loopbacks with IP addresses that will be advertised into the BGP process.