Re: MPLS Inter-AS Option A using OSPF (capability vrf-lite)

Hi Brian,

> Thanks for your response. The route that I have is nativelly advertised
> into area 24 or area 78 (see below) so it's LSA 1. What interesting is that
> when I enable capability vrf-lite just on ONE of the ASBR for example
> ASBR1, routes from CE1 get there as LSA 5, but routes from CE2 get there as
> LSA 3. So based on my labing it looks like anytime you enable "capability
> vrf-lite" on the ASBR it will always reassemble them as LSA 5s. To me it
> looks like that command not only disables PE loop prevention mechanisms,
> but at the same time disables the reassembly of any OSPF LSA 3 routes and
> just does regular redistribution.
>
>
> CE1--(OSPF)---PE1----(AS1)----ASBR1---(OSPF)--ASBR2---(AS2)---PE2---(OSPF)--CE2
>
> Area 24--->Super Area--->Area 0--->Super Area--->Area 78---
>
>
> Thanks
>
> Tom
>
>
>
> On Fri, Mar 8, 2013 at 10:24 AM, Brian McGahan <bmcgahan_at_ine.com> wrote:
>
>> If the route is Inter-Area (LSA 3) to begin with, it will be External
>> (LSA 5) on the other site. If you want it to be LSA 3 on the other site
>> then it needs to be Intra-Area (LSA 1) to begin with. You can use a
>> sham-link to maintain the route as Intra-Area over the MPLS backbone, but
>> there's really no clean way to do what you're trying to.
>>
>> HTH,
>>
>> Brian McGahan, CCIE #8593 (R&S/SP/Security)
>> bmcgahan_at_INE.com
>>
>> Internetwork Expert, Inc.
>> http://www.INE.com
>>
>>
>> -----Original Message-----
>> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>> Tom Kacprzynski
>> Sent: Friday, March 08, 2013 9:32 AM
>> To: Cisco certification
>> Subject: MPLS Inter-AS Option A using OSPF (capability vrf-lite)
>>
>> I was playing around with MPLS Inter-As option A (back to back vrf) and
>> wanted to lab all routing protocols that are used between the ASBRs on
>> their respective subinterfaces. I used eBGP, EIGRP and OSPF. I had some
>> problems with OSPF where I could not get the LSA 3 to be reassembled at the
>> other end of the VPN. This leads me to a very specific question: When
>> using OSPF in Inter-AS Option A, is it possible to reassemble the internal
>> OSPF (LSA 3) route on the other end of the VPN? I've tried it with EIGRP
>> and that worked but with OSPF I only see External LSA 5 routes.
>>
>>
>>
>> Here is a sample topology:
>>
>>
>>
>> CE--(OSPF)---PE----*(AS1)*----*ASBR1---*(OSPF)*--ASBR2*---*(AS2)*
>> ---PE---(OSPF)--CE
>>
>>
>>
>> I know that usually you would use eBGP as the routing protocol between
>> the ASBRs but I wanted to try using OSPF. The problem I'm encountering has
>> to do with "capability vrf-lite" on the PEs. When I enter that command on
>> one ASBR it doesn't reassemble OSPF routes as LSA 3 but as LSA 5. I've
>> checked the domain ID and they are matching.
>>
>>
>>
>> Based on my observation it looks like when you apply the "capability
>> vrf-lite" command on a PE(in this case the ASBR), it will always
>> redistribute OSPF routes as external LSA 5, no matter what domain-id you
>> are using.
>>
>>
>>
>> Capability vrf-lite is usually used on CEs that have OSPF running on vrfs.
>> When enabled, it disables checks like for Downward bit and domain tag.
>> Looks like another feature of this is to always redistribute M-BGP routes
>> as External LSA 5, even if domain ID matches and extended communities are
>> propagated.
>>
>>
>> Has anyone seen something like that?
>>
>>
>> Thanks
>>
>>
>> Tom Kacprzynski
>>
>>
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Received on Fri Mar 08 2013 - 11:18:13 ART