[nsp] Weird Traceroute - MPLS

[Dmitri Kalintsev]

Paul,

Lemme guess, you ran your traceroute from a cisco box that can do mpls.

Cisco (and Juniper) routers running MPLS would return MPLS label information
inside the ICMP reply packet (just capture some and have a look with
ethereal or something). The difference between the two is (IIRC) that Cisco
is using CRC value at the end of the packet and Juniper does not (uses value
of 0), so you won't see Juniper MPLS hops if you traceroute from Cisco
equipment, and vice versa. Somebody I know hacked a normal unix traceroute
so that it would decode both, and it worked pretty well (running from unix
box). :)

On Mon, Jul 12, 2004 at 09:07:35PM -0400, Paul Stewart wrote:
> I admit I don't know a lot about MPLS but can someone explain this traceroute:
> 
> Type escape sequence to abort.
> Tracing the route to www.tucows.com (216.40.32.30)
> 
>   1 gw-vlan759.nexicom.net (216.168.111.185) 4 msec 0 msec 4 msec
>   2 gw-7513.nexicom.net (216.168.96.1) 160 msec 8 msec 0 msec
>   3 dis1-toronto63-fe1-5-14.in.bellnexxia.net (206.108.110.221) 8 msec 4 msec
> 4 msec
>   4 core2-toronto63-pos1-2.in.bellnexxia.net (206.108.98.125) 8 msec 4 msec 8 msec
>   5 64.230.242.105 [MPLS: Label 12903 Exp 0] 176 msec 64 msec 8 msec
>   6 64.230.242.181 [MPLS: Label 12905 Exp 0] 4 msec 44 msec 200 msec
>   7 64.230.242.198 [MPLS: Label 12473 Exp 0] 8 msec 4 msec 4 msec
>   8 dis1-toronto12-pos6-0.in.bellnexxia.net (206.108.97.70) 8 msec 4 msec 4 msec
>   9 206.108.111.106 8 msec 4 msec 8 msec
>  10 10.78.254.125 8 msec 8 msec 4 msec
>  11 10.78.254.8 12 msec 8 msec 4 msec
>  12 129.33.183.72 8 msec 4 msec 8 msec
>  13  *  *  *
>  14  *  *  *
> 
> Why is MPLS data showing up in a traceroute?  I've never seen this before..
> 
> Thanks,
> 
> Paul
---end quoted text---

SY,
-- 
D.K.