prefix-lists

are these necessary with iBGP like they are with eBGP?

All of our devices what use eBGP have massive prefix-lists, but all of our devices that use iBGP have very short prefix lists....

I don't know much about BGP at the moment so I am still trying to figure some basic things out.

thanks

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Comments

cdad2000

Liven,

I'm sure why iBGP would be used as internal protocol, but all company needs are different. I'm not much help.

kpjungle

It could be that you dont want to advertise certain networks to your external neighbors (eBGP), but you dont mind your iBGP peers to have that information. For example if you have two ISP's you are receiving eBGP routes from, you might filter some of that information, so you dont end up being a transit path for some networks.

Also, you might want to keep some of your internal networks internal, and not advertise them to the outside world. If they are advertised by iBGP peers, your edge routers might be doing some filtering to selectively choose which ones to advertise or in what manner.

liven

Well I guess the real question is do you have to have prefix lists for routes to be learned via BGP?

kpjungle

liven wrote:

Well I guess the real question is do you have to have prefix lists for routes to be learned via BGP?

If you dont want to pass the routes to upstream BGP neighbors, you need to filter them somehow. Either by distribute-lists, route-maps or ip-prefixes. All depends on your temper i guess.