The MPLS-OPS Archive

[Spice Sylvia <falsesylvia@yahoo.co.uk>]

Perhaps am not clear,

 

1. Why would hub and spoke put things in 2 different VRFs. What does this achieve which prefix filter/Route Target filter cannot achieve?

Hub and spoke is a central site and remote side model. How does 2 VRF help?

 

2. How exciting if we had hub and spoke on the other side too?

and put routes learnt from BGP-MPLS back into IGP and then those from IGP back into BGP from vrf2 and so on.

 

We  have prefix1:rd1 from vrf1 then one from prefix1:rd2, then one from prefix1:rd3 then one from prefix1:rd4 and so on. I wonder what would be the next -hop too.

 

-S.F. 

 

Aamer Akhter <aakhter@cisco.com> wrote:

On 5/14/03 3:02 PM, "Spice Sylvia" wrote:

> Pardon me if I am not clear,
>
> Why would RD have changed?

The prefix is no longer is the same vrf.

>
> Same IP route to same prefix but why different RD?
>
> Why would one not give both to same vrf1 in hub and spoke?

Both what? Once vrf2 learns the routes from a spoke PE, it's not going to
readvertise that prefix to other spokes because of ibgp behavior. To get
around this you have to advertise the prefix to the hub PE which advertises
the prefix back to you in ANOTHER vrf. At this point, it's not the same
vpnv4 prefix, so you can export and advertise to the spoke PEs.



>
>
> Aamer Akhter wrote:
> On 5/14/03 1:58 PM, "Spice Sylvia" wrote:
>
>> Hello Aamer,
>> >> Why would the "rd" have changed?
>
> |--------1
> HUBCE HUBPE
> |--------2
>
> Suppose the sites prefixes are sent to the HUBPE, which advertises to HUBCE
> over link 2 (lets' call this vrf2), the HUBCE advertises this back to the
> HUBPE over link 1 (vrf1). vrf2 and vrf1 will have different rd's because
> they are different vrfs.
>
>>
>> Is this a new feature?
>>
>> How does changing RD help?
>>
>>
>> Aamer Akhter wrote:
>> On 5/14/03 10:51 AM, "Ferit Yegenoglu" wrote:
>>
>>>
>>> Sylvia,
>>>
>>> One possible scenario where this could happen is the hub-spoke BGP/MPLS
>>> VPN. In this case the spoke PEs advertise their routes with a Route
>>> Target value "Hub". The hub PE imports these routes and advertises them
>>> to the CE router ! in the hub site. These routes are advertised across the
>>> hub site and eventually back to the PE hub router via a different
>>> interface. The PE hub router then readvertises these routes to the spoke
>>> PEs with a Route Target value "Spoke" and a different VPN label.
>>
>> But to BGP, these "readvertised" prefixes are not the same. The rd will have
>> changed.
>>
>>>
>>> Ferit
>>>
>>>
>>>
>>>> -----Original Message-----
>>>> From: owner-mpls@UU.NET [mailto:owner-mpls@UU.NET] On Behalf Of Sugar,
>>>> Sylvia
>>>> Sent: Wednesday, May 14, 2003 10:07 AM
>>>> To: mpls-ops@mplsrc.com
>>>> Cc: mpls@UU.NET
>>>> Subject: Advertising Routes learnt from PE to PE
>>>>
>>>> Hi,
>>>> WIll a PE router ! ever advertise a route it learns from another PE
>>> router
>>>> to some other PE router.
>>>> I dont think it will ever do that as all the PE routers are IBGP peers
>>> and
>>>> would generally be in
>>>> full mesh.
>>>>
>>>> Is there any case when this might happen .. i.e. a PE router
>>> advertises a
>>>> Route learnt from one PE
>>>> to another PE. How can one do that .. because IMHO the label that will
>>> be
>>>> advertised by the former
>>>> PE router will be for the PE router to which he sends the UPDATE. How
>>> can
>>>> this PE router advertise
>>>> another PE router the same label?
>>>>
>>>> Moreover, if for some reason he has to .. does he assign a new label
>>> and
>>>>! ; then advertise?
>>>>
>>>> ANy comments on this would be very helpful!
>>>>
>>>> Silviya Sugar
>>>>
>>>> __________________________________________________
>>>> Yahoo! Plus
>>>> For a better Internet experience
>>>> http://www.yahoo.co.uk/btoffer
>>>

--
Aamer Akhter / aa@cisco.com
NSITE - cisco Systems

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