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New Member

Labels iin MPLS TE environment

I am trying to simulate a MPLS TE FRR with GNS3 and everything seems to work fine. However every time i simulate a failover, the labels seems to change

Is it something expected or a problem with the simualtion engine

When FRR is not active

R1-PE1#traceroute vrf abc 200.200.200.1
*Jan 28 20:32:21.735: %SYS-5-CONFIG_I: Configured from console by console

Type escape sequence to abort.
Tracing the route to 200.200.200.1

  1 20.20.20.2 [MPLS: Labels 209/405/607 Exp 0] 560 msec 308 msec 360 msec
  2 10.10.10.2 [MPLS: Labels 310/405/607 Exp 0] 268 msec 540 msec 204 msec
  3 10.10.10.6 [MPLS: Labels 405/607 Exp 0] 312 msec 312 msec 392 msec
  4 200.200.200.1 484 msec *  236 msec
R1-PE1#

When FRR is active

R1-PE1#traceroute vrf abc 200.200.200.1 

Type escape sequence to abort.
Tracing the route to 200.200.200.1

  1 20.20.20.2 [MPLS: Labels 209/405/607 Exp 0] 420 msec 1124 msec 712 msec
  2 30.30.30.2 [MPLS: Labels 510/405/607 Exp 0] 516 msec 480 msec 408 msec
  3 30.30.30.10 [MPLS: Labels 405/607 Exp 0] 328 msec 328 msec 220 msec
  4 200.200.200.1 648 msec *  500 msec
R1-PE1#

When i bring up my interface again

R1-PE1#traceroute vrf abc 200.200.200.1

Type escape sequence to abort.
Tracing the route to 200.200.200.1

  1 20.20.20.2 [MPLS: Labels 209/405/607 Exp 0] 372 msec 324 msec 248 msec
  2 10.10.10.2 [MPLS: Labels 312/405/607 Exp 0] 256 msec 772 msec 736 msec   .... i see lable 312 instead of 310 ??
  3 10.10.10.6 [MPLS: Labels 405/607 Exp 0] 420 msec 328 msec 344 msec
  4 200.200.200.1 312 msec *  264 msec
R1-PE1#

i have attached the configs

Ambi

Everyone's tags (1)
5 REPLIES
Cisco Employee

Re: Labels iin MPLS TE environment

Hi Ambi,

When a RSVP (or LDP) session is reset, there is no guarantee the same label used by the previous session will be allocated again for the same tunnel (or FEC) as it may have been allocated by another ressource in the meantime.

HTH

Laurent.

New Member

Re: Labels iin MPLS TE environment

Thanks Laurent

I though that but in my lab environment where i was simualting the failures, i could not think of any other resource assigning the same label

If i simulate these failures repeatedly sometimes i see the old label back so was a bit confused

Ambi

Cisco Employee

Re: Labels iin MPLS TE environment

It could happen even if there is no other ressources using label space so it's an expected behavior.

HTH

Laurent.

New Member

Re: Labels iin MPLS TE environment

thanks laurent for confirming it is an expected behavior

Ambi

New Member

Re: Labels iin MPLS TE environment

Ambi,

Have you tried the protection setting for LDP/TDP?

This is possible with "mpls ldp session protection" command. I do not know if we have this command to TDP.

Sds,

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