Re: Capability VRF Lite

Hi Carlos
I agree with the first point in that the down bit is used to prevent loops
in mpls backbone but on the
second point, I have tested this a few times with same result.

However having played about with this more since your last email I have
found the following results.

If the CE is running VRFs and is configured with ospf multi-vrf towards PE
we effectively extend the MPLS Superbackbone all the way to the CE,
therefore the loop prevention on the PE kicks in and the CE receives routes
with down bit set.

CE1#sh ip ospf 2 | i Superbackbone
 Connected to MPLS VPN Superbackbone, VRF VPN_A
155.1.58.0 is a prefix at the remote CE site
CE1#sh ip ospf database summ 155.1.58.0

            OSPF Router with ID (155.1.67.7) (Process ID 2)

                Summary Net Link States (Area 1)

  Routing Bit Set on this LSA
  LS age: 776
  Options: (No TOS-capability, DC, *Downward) I have made a big assumption
here that Downward means the Down bit has been set, feel free to shoot me
down.*

I started by configuring capability vrf-lite on the PE and this solved the
issue of the CE installing routes in the routing table for
the particular VRF.
However this stops the PE from connecting to the Superbackbone, which is
obviously not a good idea.
Before capability vrf-lite
PE1#sh ip ospf 2 | i Superbackbone
 Connected to MPLS VPN Superbackbone, VRF VPN_A
After capability vrf-lite
PE1#sh ip ospf 2 | i Superbackbone
PE1#

Therefore configuring capability vrf-lite on the CE would be the correct
behaviour because this allows routes recieved from the PE to be correctly
installed
in the routing table even if they have the down bit set and also disconnects
the CE from the MPLS Superbackbone.

Everything I have written here is just what I observed when testing this so
please can one of the experts clarify?

Thanks in advance.

On 31 May 2010 19:54, Carlos G Mendioroz <tron_at_huapi.ba.ar> wrote:

> > Therefore CE1 can see these routes in ospf database with down bit set
> > and never installs them in routing table.
>
> I don't think this is the way it works. The down bit is used to prevent
> loops in the mpls backbone. The CE sould use those routes w/o problem.
>
> -Carlos
>
> Muzammil Malick @ 31/5/2010 14:42 -0300 dixit:
>
>> So I am running VRF lite on CE1 and peering via ospf to PE1.
>> When PE1 redistributes bgp routes from remote site into OSPF and
>> propagates them to CE1 they are sent as summary LSAs with the Down bit set.
>> Therefore CE1 can see these routes in ospf database with down bit set and
>> never installs them in routing table.
>> However by setting capability vrf-lite on PE's ospf vrf process, the PE
>> now sends route as external LSAs and to my understanding these LSAs are
>> excepted from the Down bit check
>> and are sent to CE1 as normal. CE1 now sees these as external LSAs and
>> installs them in its routing table (VRF).
>>
>>
>> On 31 May 2010 18:33, Carlos G Mendioroz <tron_at_huapi.ba.ar <mailto:
>> tron_at_huapi.ba.ar>> wrote:
>>
>> Would you please tell me what "problem" is that you solved ?
>> -Carlos
>>
>> Muzammil Malick @ 31/5/2010 9:21 -0300 dixit:
>>
>> Hi
>>
>> I have been studying the use of the capability vrf-lite command
>> and I
>> was wondering whether there is any difference/issue
>> when configuring this on the PE or CE.
>>
>> For example my PE is redistributing BGP into OSPF and sending
>> OSPF routes to
>> CE with down bit set. So I configured capability vrf-lite
>> command on PE and this solved the problem. But I read somewhere
>> that
>> this should be configured on the CE.
>>
>>
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>>
>>
>> -- Carlos G Mendioroz <tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar
>> >>
>> LW7 EQI Argentina
>>
>>
>>
> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina

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Received on Mon May 31 2010 - 20:54:45 ART