[c-nsp] traceroute shows mpls labels...how?

[Roger Wiklund]

MPLS TTL

By default mpls ip propagation-ttl is enabled in global configuration
mode. This enabled user to trace the hops of the mpls router with
labels as shown in above traceroute. This is because MPLS TTL field is
copied from IP TTL field, on each MPLS LSR hop a TTL will be
decremented.

To “hide” the MPLS hops you can disable it by doing no mpls ip
propagation-ttl on every LSR in global configuration mode. Disabling
MPLS propagation TTL will make MPLS TTL field to have a fixed 255
value, and on every MPLS LSR hop the IP TTL value will be intact. IP
TTL will only be decremented when egress LSR sends out to the
destination host unlabeled.

m1(config)#no mpls ip propagate-ttl

Not sure why you're not seeing it in Windows, prob a very simple
traceroute implementation.

/Roger

On Wed, Aug 22, 2012 at 9:21 PM, Aaron <aaron1 at gvtc.com> wrote:
> Do you all know how this works?  How is traceroute able to report back the
> mpls label that is in use in the transit hops?  Also wondering why I don't
> see this on windows command line tracert
>
>
>
> Aaron
>
>
>
>
>
> RP/0/RSP0/CPU0:9k#trace vrf one 1.2.3.4 source 2.4.6.8
>
>
>
> 1  19.1911.5 [MPLS: Labels 16001/16220 Exp 0] 2 msec  1 msec  0 msec
>
> 2  19.1911.1 [MPLS: Label 16220 Exp 0] 0 msec  0 msec  1 msec
>
> 3  88.88.191.22 0 msec  0 msec
>
>     19.1911.33 1 msec
>
> 4  88.88.191.18 1 msec  1 msec  0 msec
>
> 5  88.88.135.221 10 msec  10 msec  11 msec
>
> 6  122.47.236.130 [MPLS: Label 17039 Exp 1] 47 msec  49 msec  51 msec
>
> 7  122.47.154.53 [MPLS: Labels 0/17017 Exp 1] 48 msec  49 msec  47 msec
>
> 8  122.45.30.134 [MPLS: Labels 23417/17016 Exp 1] 48 msec  49 msec  47 msec
>
> 9  122.45.1.17 [MPLS: Labels 23439/17016 Exp 1] 50 msec  49 msec  51 msec
>
> 10 122.45.31.189 [MPLS: Labels 0/17016 Exp 1] 51 msec  54 msec  51 msec
>
> 11 122.45.158.34 [MPLS: Labels 0/16009 Exp 1] 49 msec  50 msec  47 msec
>
> 12 122.45.104.49 46 msec  46 msec  47 msec
>
> 13 122.45.108.14 47 msec  47 msec  47 msec
>
> 14  *  *  *
>
> 15  *  *  *
>
> 16  *
>
>
>
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