From: Victor Cappuccio (vcappuccio@gmail.com)
Date: Thu Oct 16 2008 - 13:18:18 ART
Hi Ovais,
can you please post your topology, and a couple of show indicating where you
see the problem,
show mpls inter
show mpls ldp neigh
show mpls ldp disco
show mpls forwarding
in this link http://www.ciscopress.com/articles/article.asp?p=680824
you can find the the label operation by
*Pop: *The top label is removed. The packet is forwarded with the remaining
label stack or as an unlabeled packet.*
Swap: *The top label is removed and replaced with a new label.*
Push: *The top label is replaced with a new label (swapped), and one or more
labels are added
(pushed) on top of the swapped label.*
Untagged/No Label: *The stack is removed, and the packet is forwarded
unlabeled.*
Aggregate: *The label stack is removed, and an IP lookup is done on the IP
packet.
an example
http://anetworkerblog.com/2008/05/10/csc-mpls-vpn-triple-stack/
another example:
http://anetworkerblog.com/2008/05/10/csc-mpls-vpn-triple-stack/
How LDP Works.
http://anetworkerblog.com/2008/08/10/ldp-transport-address/
How to prevent Rogue LDP Devices.
http://anetworkerblog.com/2008/08/15/rouge-mlpsdev/
HTH
Victor.-
On Thu, Oct 16, 2008 at 5:30 PM, Ovais Iqbal <ovais.iqball@yahoo.com> wrote:
> hi all, how are you, i just have a simple MPLS query
> see i have 3 routers connected serially to each other.
>
> on R1 what i did, i made a loopback, a serial interface serial 1/0 with no
> keepalive to take it to up state and another serial link serial 1/2
> connected
> to R2.
> I just enabled mpls ip on serial connected to R2 and ran ospf on all
> links.This is wat i got when i ran show mpls forwarding-table on R1
>
> for loopback my outgoing label or vc was UNTAGGED !!!!!
> for my serial (no keepalive) it was POP TAG !!! Why is that so ??
>
> where will i see untagged ?? i heard someone saying that we will see
> untagged
> on interface that are not running mpls, but i m not running mpls on
> serial1/0
> then why am i seeing pop tag on serial 1/0 ?? shouldnt it be UNTAGGED ?
> Kindly clear my confusion ? pls explain me when i should be seeing untagged
> and when pop tag, i am a totally new bie so pls explain it to my level as
> you
> did before Thanks
>
>
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-- Victor Cappuccio CCIE R/S# 20657 CCSI# 30452 www.anetworkerblog.comBlogs and organic groups at http://www.ccie.net
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