BGP Multihoming/FullorPartial routes

[Ibrahim Jamil]

Hi Experts

in a multihoming envirments when and why an enterprise request fom its provider full or partial routes?

here in my contry i only see default-routes from ISPs

thanks

thanks cisco for netpro

jamil

[Sergey Fer]

BGP is not OSPF-like. It has no embedded paranoid update timer or something like that. If two BGP peers established session, they only send keepalives to each other. If you (or your peer) add or remove route you (or peer) send Update message to add or withdraw routes.

Sometimes you need to change your inbound policy concerning some peer and therefore you must refresh updates. There are 3 possible ways to do it. First - you may reset your BGP session, it leads to network instability. Second - you may store your peer's updates locally (soft reconfiguration), it obviously requires additional memory. And the third way - use Route Refresh Capability. It is a feature that must be negotiated between two peers during initial session start up. If they agree about it then they may use Refresh. It allows BGP router to ask peer to resend it's NLRI if it is neccessary (due to policy change or something like that).

[Dan-Ciprian Cicioiu]

Hi Ibrahim , Sergey,

I think that Ibrahim question is related to the global internet routing table and default route advertisement.

If you have only 2 links to the internet , I do not think having the global internet routing info will help you much, for sure it will consume you alot of memory Generelay speaking will help to control the outgoing traffic to the internet. I know some small ISPs that are using default routing.

Dan

[Ibrahim Jamil]

thanks