This is a book about connecting to the Internet as reliably as possible. This means
eliminating all single points of failure,including having just one Internet service provider
(ISP). By multihoming to two or more ISPs,you can remain connected when
either ISP (or your connection to them) experiences problems. However,there is a
catch: if you are a regular customer,your ISP makes sure your IP addresses are
known throughout the Net,so every router connected to the Internet knows where
to send packets addressed to your systems. If you connect to two ISPs,you’ll have to
do this yourself and enter the world of interdomain routing via the Border Gateway
Protocol (BGP). The majority of this book deals with BGP in a practical,hands-on
My involvement with BGP started in 1995,when I entered a darkened room with a
lot of modem lights blinking and was told,“This box connects to both our ISPs,but
it doesn’t do what we want it to. Maybe you can have a look. It’s called a Cisco. Here
are the manuals.” It didn’t take me long to figure out that we needed to run BGP to
make this setup work as desired,but getting information on how to do this properly
was a lot harder: very little of the available BGP information takes actual interdomain
routing practices into account. In this book,I intend to provide an insight into
these practices,based on my experiences as a network engineer working for several
small multihomed ISPs and a large ISP with many multihomed customers,and as a
consultant in the area of routing in general and interdomain routing in particular.
Border Gateway Protocol (BGP) is the routing protocol used to exchange routing information across the Internet. It makes it possible for ISPs to connect to each other and for end-users to connect to more than one ISP. BGP is the only protocol that is designed to deal with a network of the Internet's size, and the only protocol that can deal well with having multiple connections to unrelated routing domains.
This book is a guide to all aspects of BGP: the protocol, its configuration and operation in an Internet environment, and how to troubleshooting it. The book also describes how to secure BGP, and how BGP can be used as a tool in combating Distributed Denial of Service (DDoS) attacks. Although the examples throughout this book are for Cisco routers, the techniques discussed can be applied to any BGP-capable router.
The topics include:
Requesting an AS number and IP addresses
Route filtering by remote ISPs and how to avoid this
Configuring the initial BGP setup
Balancing the available incoming or outgoing traffic over the available connections
Securing and troubleshooting BGP
BGP in larger networks: interaction with internal routing protocols, scalability issues
BGP in Internet Service Provider networks
The book is filled with numerous configuration examples with more complex case studies at the end of the book to strengthen your understanding. BGP
is for anyone interested in creating reliable connectivity to the Internet.