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Chapter 18. BGP
18.1. What is BGP?
BGP (Border Gateway Protocol) is the protocol used between ISPs to advise peers of routes that are available.
Each ISP tells its peers the routes it can see, being the routes it knows itself and those that it has been advised
by other peers.
In an ideal world everyone would tell everyone else the routes they can see; there would be almost no
configuration needed; all packets would find the best route accross the Internet automatically. To some extent
this is what happens between major transit providers in the Internet backbone.
In practice things are not that simple and you will have some specific relationships with peers when using BGP.
For most people there will be transit providers with which you peer. The FB2700 cannot take a full table (map
of the whole Internet) from a transit provider so you would typically have a default route to them. You can
advise the transit provider of your own routes for your own network so that they can route to you, and they tell
their peers that they can route to you via that provider. This only works if you have IP address space of your
own that you can announce to the world - unless you are an ISP then this is not commonly the case.
Even though IPv4 address space has already run out, it is possible to obtain IPv6 PI address space and an AS
number to announce your own IPv6 addresses to multiple providers for extra resilience.
You can use BGP purely as an internal routing protocol to ensure parts of your network know how to route to
other parts of your network, and can dynamically reroute via other links when necessary.
In most cases, unless you are an ISP of somesort, you are not likely to need BGP.
18.2. BGP Setup
18.2.1. Overview
The FB2700 series router provides BGP routing capabilities. The FB2700 cannot handle a full table. The aim
of the design is to make configurationm simple for a small ISP or corporate BGP user - defining key types of
BGP peer with pre-set rules to minimise mistakes.
Caution
Misconfiguring BGP can have a serious impact on the Internet as a whole. In most cases your transit
providers will have necessary filtering in place to protect from mistakes, but that is not always the case.
If you are an ISP and connect to peering points you can cause havoc locally, or even internationally,
by misconfiguring your BGP. Take care and get professional advice if you are unsure.
18.2.2. Standards
The key features supported are:-
• Simple pre-set configurations for typical ISP/corporate setup
• RFC4271 Standard BGP capable of handling multiple full internet routing tables
• RFC4893 32 bit AS number handling
• RFC2858 Multi protocol handling of IPv6
• RFC1997 Community tagging, with in-build support of well-known communities
• RFC2385 TCP MD5 protection