An introduction to BGP.

In this update I want to start one of the protocol/technology tracks that I will continue over time, hopefully building into a library of topics on what is really quite a big subject.

I've started with BGP rather than some of the simpler or more familiar protocols because to me, its a crucial protocol to learn.

BGP is effectively what ties the Internet together and what stops it being a loose association of networks and (combined with things like the DNS process) allows traffic to get from your machine to wherever it needs to go.

It allows service providers to not only run their network but also to allow you tell the world where your address space is and how to find theirs.

The other reason I've decided to start with this is that it is a fundamental importance in MPLS VPNs via VPNV4 address schemes. (it is worth noting at this point that all my documents are in the IPV4 world and IPV6 versions will come in due course). Label switching itself is an independent process but in order to get true MPLS VPN's to work, you need to overcome a few functions with BGP allows (this will be covered cross topics on this and the MPLS sections).

BGP is very similar to some of the more basic LAN routing protocols but comes from a LAN heritage (the IGP function) and is the effective merger of IGP and EGP.

Whilst many service providers over the years used IS-IS to cover their domain in some cases or OSPF in others, BGP has become the front runner for more than just the network edge. It is also possible to use BGP to merge different networks together which use alternative routing protocols.

The plan is to break down BGP into a number of smaller bits, Once this loose introduction is complete we'll start with BGP101: The basics. In that segment i'll cover the basic formation of BGP and how it sets up its relationships with other devices, how it holds its information.

Next I'll cover BGP Neighbor relationships, in which we'll look at what to do once a basic relationship is setup, how to do so, how to leverage information from it etc.

I also want to cover modules on BGP Route tables, BGP traffic shaping, VPNV4 addressing for BGP, BGP troubleshooting and general BGP CLI corner.

As ever if you have any questions, either add them in the comments or email me.