rfc4271 ORIGIN/path of default route, should the value be 0 or 2?

Tue Jul 7 17:57:27 UTC 2020

Okay,

In my use case it's just a default route being distributed by a router that has the full routing table to an access router in the same ASN. It's not being sent to other ASNs or anything of that sort.

I was just curious as to why Cisco sets it to internal and Arista sets it to invalid.

Thanks,
-Drew

-----Original Message-----
From: NANOG <nanog-bounces+drew.weaver=thenap.com at nanog.org> On Behalf Of Olivier Benghozi
Sent: Tuesday, July 7, 2020 12:47 PM
To: nanog at nanog.org
Subject: Re: rfc4271 ORIGIN/path of default route, should the value be 0 or 2?

Debatable, certainly, as the Origin attribute should probably be considered as dead/obsolete and therefore it is probably a good practice to always set/reset it to internal.
A number of networks already do this (including level3 by example).

After all, the origin attribute was only designed to allow a «smooth» transition between EGP and BGP (that is, it was useful during a few years for a few networks several decades ago).

> Le 7 juil. 2020 à 15:47, Saku Ytti <saku at ytti.fi> a écrit :
> 
> Debatable, but:
> Internal is more accurate if you redistribute default from routing 
> protocol, such as static.
> Unknown is more accurate if you just generate it in BGP, without having it.
> 
> Functional difference is best-path selection algorithm. Origin can be 
> used to bypass hot-potato policies of peers, by forcing them to carry 
> packets longer inside their network. If your policy is hot-potato, 
> then you should reset Origin on received external routes.