Nugget 20
BGP Routing - Implementing Basic BGP 1

An Autonomous System (AS) is the foundation of everything ,it represents the networks under
1 authority.


There are public AS's and private AS's

IBGP = a relationship between 2 BGP speakers in the  same AS
EBGP = is used when the two routers are different AS's (like the BGP relationship you would have if you were to peer with your ISP)

NEED to make mind change, as neighbours are now redefined .... as opposed to how we think of them with other routing protocols

Neighbours DONT have to be directly connected! they can form through routers! becuase BGP rides ONTOP of your existing network infastructure...say OSPF/EIGRP etc

USUALLY BGP does NOT REPLACE an internal routing protocol, it really is used to establish relationships with the outside world.

Thru this relationship the ISPs can exchange routes via you, so this means they end up using you as a path to reach each the other ISP (so you are a transit AS)

You can solve this by redistribution, but interior routing protocols are not designed to handle hundreds of megabyte's of routing tables, OSPF wont handle it etc ... so although this is not WISE, you can do this if you redistribute a small subset of networks

You could also bring up a WAN link between these two routers (IBGP) to directly connect them to solve this problem .... or you could run BGP on the other router ... but this needs to be able to support the hardware requirements etc ...