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RE: mpls label stack with TE and VPN posted 11/06/2008
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You'd need to run LDP on TE tunnel when your TE tunnel endpoint is on a P router instead of PE. In those situations TE will pop TE label on a router upstream from the P router. The P router will get a frame with just MPLS VPN label. P router doesn't know what to do with it.

If you add LDP on top of TE, P router will introduce another LDP label to reach next hop and advertise it to the TE headend router. This label will be added in between TE label and MPLS VPN label. The TE tailend router (P router) will see frames with 2 labels, LDP label and MPLS VPN label. It will pop LDP label and forward it to PE router.







Roman Rodichev
5xCCIE #7927 (R&S, Security, Voice, Storage, Service Provider)
Instructor, Content Developer. ieMentor Corporation
http://www.iementor.com
Y!M: roman7927

-----Original Message-----
From: "Rich Collins" <nilsi2002@xxxxxxxxx>
To: "Roman Rodichev" <roman@xxxxxxxxxxxx>
Cc: "abderrahim sadki" <a_sadki1@xxxxxxxxxxx>; ccielab@xxxxxxxxxxxxxx
Sent: 11/6/08 8:57 AM
Subject: Re: mpls label stack with TE and VPN

Hello Roman,

I have seen that last version you mentioned in certain examples.

So in what situation or what is the advantage of putting "mpls ip" on the TE
tunnel interface?

Thanks
Rich


On Thu, Nov 6, 2008 at 12:53 AM, Roman Rodichev <roman@xxxxxxxxxxxx> wrote:

> TE is independent of LDP. Your MPLS VPN destinations are forwarded based on
> the bgp next-hop loopback address. How you MPLS forward to that loopback,
> using TE or LDP, is up to you. If TE tunnel is up, it will use TE label. If
> TE tunnel is down and LDP is working, it will use LDP label.
>
> You don't need to run LDP in order to use TE. In fact, you could remove
> "mpls ip" configuration from all interfaces, and just use TE between PE's,
> and your MPLS VPN would still work.
>
> Finally, you could actually run LDP on top of TE tunnel (configure "mpls
> ip"
> on the TE tunnel interface). Now you'll see three labels. TE label on top,
> LDP label in the middle, MPLS VPN label on the bottom
>
>
>
> Roman Rodichev
> 5xCCIE #7927 (R&S, Security, Voice, Storage, Service Provider)
> Instructor, Content Developer
> ieMentor Corporation http://www.iementor.com
> Y!M: roman7927
>
> -----Original Message-----
> From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
> abderrahim sadki
> Sent: Wednesday, November 05, 2008 11:41 PM
> To: ccielab@xxxxxxxxxxxxxx
> Subject: mpls label stack with TE and VPN
>
> Hi,
>
> I thought that when using MPLS TE with VPN I would end up with 3 labels in
> the
> packets(LDP-TE-VPN).
> But from the Cisco books and lookig and packets on wireshark I see only 2
> labels.
>
> why is that? and when should I see 3 labels, is it when the tail of the TE
> tunnel is not the same as the tail of the VPN tunnel?
>
> Thanks,
> Abderrahim
>
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