From: Piotr M (pitt2k@gmail.com)
Date: Mon Dec 29 2008 - 14:22:37 ARST
Vignesh,
Yes, so my understanding is as follows:
If a customer has OSPF Area 0 connected together thru MPLS network
(provided by SP), there are some rules you need to be aware of:
1. Process ID matching - as you know the OSPF process ID is a locally
significant thing, but here, it is important if the process ID on PE
routers is the same or not. If not (SP could not assign the same
process ID on both PEs for some reason), the Intra-Area routes will be
translated to External (E2) routes on the far end. This is based on an
attribute called Domain-ID which is send to the far end PE by MPBGP
and it is based on Process ID. So if process ID is different on both
PEs, you can manually set Domain-ID using "domain-id 1.2.3.4" command.
2. LSA translation - if you connect two OSPF Areas 0 together (and the
process-id is the same or domain-id is the same), the PE routers
translate all Intra-Area routes to Inter-Area (IA) routes. The
External (E1/E2) routes are not translated. In this case the MPLS
network becomes "superbackbone" as it is backbone of customer's
network (customer's Area 0 is a backbone already). Then, if you want
to see customer's prefixes not touched (Intra-Area still will be
Intra-Area on the far end router) you need to configure something
called Sham-link, which is basically similar to Virtual-link and it's
going between PE routers. Configuration is simple, just create new
loopback interfaces on both PEs, add them to VRF and advertise into
MPBGP. Once they are accessed on both PEs, you can use those addresses
to create sham-link using command: area 0 sham-link 1.2.3.4 5.6.7.8.
That's all folk!
HTH,
PM
2008/12/29 Vignesh Sethuraman <sethuvignesh@gmail.com>:
> Hi Piotr,
>
> Yes, OSPF running on customer sites and how those routes are redistributed
> into MP-BGP, propagted in MPLS VPN backbone and then again redistributed
> back into OSPF again.
>
> Regards,
> Vignesh
>
> On Mon, Dec 29, 2008 at 9:22 PM, Piotr M <pitt2k@gmail.com> wrote:
>>
>> Hi Vignesh,
>>
>> What do you mean by "superbackbone"? Are you referring to OSPF between
>> PE-CE and MPLS Cloud as a new backbone for this design?
>>
>> Regards,
>> PM
>>
>> 2008/12/29 vignesh sethuraman <sethuvignesh@yahoo.co.in>:
>> > Hello Experts,
>> >
>> > Could you please someone clarify the use or need of superbackbone in the
>> > MPLS
>> > VPN service. And kindly explain me how that works.
>> >
>> > Thanks In Advance.
>> >
>> > Regards,
>> > Vignesh
>> >
>> >
>> >
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