Re:OSPF Duplicate Router-id - problem areas

Generally people define a loop back as rid, using the same interface for
device management. Using duplicate rids is taking a risk without any
benefit. The rid does not need to exist as an ip, so using duplicates
wouldn't even save addresses. Even if you were to have a topology where
duplicate rids were not causing problems, they may do so when that network
is later modified.
 On Dec 22, 2011 5:41 AM, "Tom Kacprzynski" <tom.kac_at_gmail.com> wrote:

> Hello,
> I have a quick question regarding OSPF Router-id uniqueness. I know that
> router-id needs to be unique in OSPF. So I did some testing.
>
> Looks like in the same area you'll run into problem.
>
> I'm thinking that if you have virtual-links, then yeah that would give your
> problems.
>
> You can't have any ABR or ASBR with router-id that are duplicate, that is a
> problem for sure.
>
> In you have member routers in different areas with duplicate router-id,
> you'll run into problems if one of the routers sharing the same router-id
> is originating an external route (FLOOD_WAR).
>
> But outside of that, everyone else would see the advertising router as ABR
> and not the router with duplicate router-id so that should be ok.
>
> Are there any other scenarios? Seems to me saying that the whole AS needs
> to have unique router-id might be too general and there are few cases where
> you won't need that. I'm not saying to start configure them duplicate, but
> just exploring the concept further.
>
>
> Thank you very much in advance for any input.
>
> Tom Kacprzynski
>
>
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Received on Thu Dec 22 2011 - 12:18:40 ART