[c-nsp] Does traffic routing through a PE get an MPLS label added/removed?

Tim Franklin tim at pelican.org
Tue Dec 2 07:15:15 EST 2008

On Tue, December 2, 2008 10:48 am, TiM wrote:

> Can anyone point me to Documentation that would answer this question?
> I'm sure that ingress traffic is assigned some internal "you're in VRF x"
> label, but our SE was clear in stating it would be an MPLS header added
> and removed, the same information as if it was egressing towards Site 2/3.

Documentation, no, but an example seems to support that CEF is *not* going
to impose and remove a label:

For a route on the same PE, same VRF:

router#sh ip cef vrf xxx x.x.x.8 detail
x.x.x.8/32, epoch 1
  local label info: other/759
  recursive via x.x.x.66
    recursive via x.x.x.x/30
      attached to Serial4/0/0.1/1/3/2:0

Same VPN, other PE:

router#sh ip cef vrf xxx x.x.x.121 detail
x.x.x.121/32, epoch 1
  recursive via x.x.x.56 label 67
    nexthop x.x.x.34 TenGigabitEthernet9/1 label 16071

Whether some kind of recirculation happens inside the box where it puts a
label on and then takes it off again, I don't know, but I absolutely agree
that it sounds somewhat strange.


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