RE: [OSL | CCIE_SP] When exactly do you need the "mpls bgp

The purpose of exchanging label in L3 VPN is for a PE router knows which
label to use to reach the other-end PE. Thus, the selected option depends on
which PE routers you are establishing MP-eBGP.
Rin

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of Rich
Collins
Sent: Tuesday, June 02, 2009 10:13 AM
To: Bryan Bartik
Cc: Rick Mur; Cisco certification
Subject: Re: [OSL | CCIE_SP] When exactly do you need the "mpls bgp
forwarding" command?

 I've been a little curious about this myself.

 So what is the difference here between the 'send-label' or just
 enabling mpls on both back-to-back interfaces? What clue would tip
 you off that one is expected and not the other...i.e. what do you get
 with one but not the other method?

Thanks
 Rich
>
> On Mon, Jun 1, 2009 at 4:50 PM, Bryan Bartik <bbartik_at_ipexpert.com> wrote:
>> Rick,
>>
>> Thanks for the explanation. The guide I was following was using S train,
>> while I was on the "normal" train, so that does make sense. Thanks,
>>
>> On Mon, Jun 1, 2009 at 2:46 PM, Rick Mur <rick_at_rickmur.com> wrote:
>>
>>> Since you are using a back-to-back configuration (RFC2547bis option A
for
>>> the freaks ;-), there is no need for exchanging labels with the other
end.
>>> The 'mpls bgp forwarding' command is only available in 12.xS trains, so
you
>>> would see it only on 7200 series. Then again, it will be automatically
put
>>> on the interface if you put the 'send-label' on a BGP neighbor.
>>>
>>> So again, you don't need to exchange labels with this kind of
back-to-back
>>> connectivity.
>>>
>>>
>>> Rick Mur
>>> CCIE2 #21946 (R&S / SP)
>>> rick_at_rickmur.com

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Received on Tue Jun 02 2009 - 11:23:12 ART