BGP Question

[James Hoggard]

Hi,

I currently work for an ISP and also studying BGP. I was wondering when an ISP peers with another ISP what is the most common or best way for an ISP to advertise there networks. They obviously can't use the network commend as you could have 1000's and 1000's of routes will they use a routes map and apply this outbound and the route match matches a prefix list?

What options do you have here?

[Richard Burts]

The most common way for an ISP to advertise their networks is that they advertise routes/prefixes that they have learned from others. When they have learned routes/prefixes from one EBGP peer then they can advertise those to other BGP peers (no network statement required). And when they have learned routes/prefixes from their customers they may aggregate or summarize those routes and advertise the results to BGP neighbors. They would need network statements only for the networks whose advertisement is started from that ISP.

HTH

Rick