BGP Route Selection - Attribute Origin

cisco2003 · ‎11-04-2005

A route receive a route from ospf, for example 10.1.1.0/24. Now I advertise it into BGP by two ways at same time:

1. network 10.1.1.0 mask 255.255.255.0

2. redistribute ospf 1

So in BGP table, the winner should have attribute Origin with "?" or "i" ? And why?

In what step is the winner produced ?

And please give me any RFC info about this if anybody know. Thanks a lot.

ruwhite · ‎11-04-2005

I just tried it, doing redistribute first, then the network statement, and then the network statement first, then redistribution. The result in both cases is the BGP route has an origin attribute of "i." I don't know why, for certain, why one would be preferred over the other, other than the normal rule of i's being preferred over ?'s in the origin attribute.

HTH.

Russ.W

cisco2003 · ‎11-07-2005

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml

Here is a topic about BGP path selection on Cisco website. For my above question, I am not sure in what step the winner is arbitrated, Step 3 or 5 ?

I checked draft-ietf-idr-bgp4-26.txt

( http://www.ietf.org/internet-drafts/draft-ietf-idr-bgp4-26.txt ), but I can not find related specification. So what is cisco's behavior and bases on this point?