Thanks Roger, I knew about that. But what I was asking is how does that label information get reported back to the device that I'm doing the traceroute from.... you see what I'm asking ?
I might put a sniffer on the device that I'm tracing from to look at that icmp ttl expired in transit packets and see where exactly is that label information embedded/carried in the ttl expired in transit packets..... see what I'm asking ? Aaron -----Original Message----- From: Roger Wiklund [mailto:[email protected]] Sent: Wednesday, August 22, 2012 2:49 PM To: Aaron Cc: [email protected] Subject: Re: [c-nsp] traceroute shows mpls labels...how? 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 <[email protected]> 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 * > > > > _______________________________________________ > cisco-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
