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New Member

#no mpls ip propagate-ttl cmd question-?

Hi:

When this cmd. is enabled both on PE1 and PE2 across a MPLS core, why does the trace output show the egress PE2 router in the output?

I have CE1->PE1->P->PE2->CE2.

I am tracing to the lo0 of CE2 10.1.8.8

PE1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

PE1(config)#no mpls ip propagate-ttl

PE1(config)#end

PE2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

PE2(config)#no mpls ip propagate-ttl

PE2(config)#end

CE1#tr ip 10.1.8.8

Type escape sequence to abort.

Tracing the route to 10.1.8.8

1 10.1.17.1 28 msec 28 msec 28 msec

2 10.1.58.5 168 msec 180 msec 168 msec

3 10.1.58.8 112 msec * 112 msec

CE1#

As you can see, 10.1.58.5 is the PE2 intf. to CE2. I was hoping to see only 2 hops.

Now the doc for this cmd does say that it sometimes shows the egress provider router.

Is this based on IOS or router model?

Or just another bug ;->

Thx.

2 REPLIES
Cisco Employee

Re: #no mpls ip propagate-ttl cmd question-?

Niraj,

This is normal behavior. This command will hide the SP core except for the ingress and egress PE.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: #no mpls ip propagate-ttl cmd question-?

Thanks Harold!!

I was going by the example shown in the pdf for MPLS Technology Essentials where they only showed 2 hops, the 1st PE and then CE2 and thus....(they did state that sometimes the egress PE would also show up)....

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