[c-nsp] VASI interfaces on IOS XR

[Nick Ryce]

Completely agree.  Thanks for the insight.

Nick

On 22 Feb 2012, at 08:22, "Bruce Pinsky" <bep at whack.org> wrote:

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> Nick Ryce wrote:
>> Hi Bruce,
>>
>> I was hoping to have an easy way out from import / export :-)
>>
>>
>
> In the VASI scenarios I've seen, BGP is used to send routes learned from
> the MP-BGP sessions to the the PE-CE BGP sessions and vice versa.  So, in
> essence, you have three different BGP domains, the PE-CE, the MP-BGP, and
> the inter-VASI.  In effect, you have two different "redistributions" going
> on.  This is the result of having the VASI interfaces "shimmed" between the
> real interfaces facing the CE and the P/PE MPLS core.
>
> Since you don't need the VASI construct as you are not trying to apply
> services to a label switched interface, I don't think you need the
> complexity of what VASI introduces.  If you simply need to get routes from
> one VRF to another, I think that you should be able to do something like this:
>
> router ospf 1
> redistribute ospf 2 vrf bar
>
> router ospf 2
> redistribute ospf 1 vrf foo
>
> I know that VRF aware redistribution is available in IOS, but not sure
> about XR (didn't spend a lot of time hunting through the docs).  To me the
> downside of redistribution is that you end up with external routes but
> perhaps that's not an issue in your environment.
>
> Import/Export may seem like a pain, but I don't think anymore so than
> mutual redistribution and the access-lists and/or tags to prevent loops.
>
> I suppose you could get fancy and use BGP between VASI interfaces and
> redistribute your OSPF into BGP to get it across.  But I think it violates
> the KISS and 2am principles unnecessarily.
>
> - --
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