[c-nsp] Label still appearing in traceroute after disabling ttl propagation

[John Neiberger]

I guess I should rephrase. We have configured "mpls ip-ttl-propagate
disable" to try to hide the labeled part of the path. For whatever reason,
we always get something like the following:
CE1#trace 10.6.10.1 source lo0
Type escape sequence to abort.
Tracing the route to 10.6.10.1
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.105.50 0 msec 0 msec 0 msec
  2 192.168.62.2 [MPLS: Label 16018 Exp 0] 4 msec 0 msec 0 msec
  3 192.168.62.60 0 msec 0 msec 0 msec
  4 192.168.106.61 4 msec *  0 msec
CE1#
If I trace from CE1 to the loopback of PE2, which is the same path, it
works as expected and the labeled part of the path is hidden:

CE5#trace 10.6.1.1 source lo0
Type escape sequence to abort.
Tracing the route to 10.6.1.1
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.105.50 4 msec 0 msec 0 msec
  2 192.168.62.60 0 msec *  0 msec


On Tue, Jul 30, 2013 at 11:43 AM, Jared Mauch <jared at puck.nether.net> wrote:

> Disable TTL != don't copy label into ICMP TTL Expired message.
>
> - Jared
>
> On Jul 30, 2013, at 1:37 PM, John Neiberger <jneiberger at gmail.com> wrote:
>
> > I think either we're just doing something wrong or perhaps we're running
> > into a bug. I did find this one, which sounds similar:
> >
> > https://tools.cisco.com/bugsearch/bug/CSCtd17126
> >
> > I'm not sure if that is fixed in 4.1.0 or not.
> >
> >
> > On Tue, Jul 30, 2013 at 11:01 AM, John Neiberger <jneiberger at gmail.com
> >wrote:
> >
> >> W
> >> e're running into an interesting problem. We have a simple lab setup
> like
> >> this:
> >>
> >> CE1 -- PE1 --- P1 --- P2 --- PE2 --- CE2
> >>
> >> We have "mpls ip-ttl-propagate disable" on all PE and P routers, but if
> we
> >> trace from CE1 to CE2, we still see an MPLS label coming from the PE2
> >> router. If we trace CE2 to CE1, we see a label on the hop from P1 to
> PE1.
> >>
> >> If we have ttl propagation completely disabled, why would we still see
> the
> >> label and P-to-PE link in the path?
> >>
> >> All P and PE routers are IOS XR running 4.1.0.
> >>
> >> Thanks,
> >> John
> >>
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