Re: no mpls ip propagate-ttl forwarded

Hi Jacek,

This is expected. I assume you haven't put your CE routers into an MPLS VPN.

We've got to remember MPLS Penultimate-hop-Popping (PHP) is enabled by
default. Because of that R4 gets an unlabeled packet from R3. This is
because 10.1.45. network is directly connected to R4. Because it is an
unlabeled packet, R4 process the packet normally decrementing the TTL by
one.

Hope this helps!!!

Sud.

On Thu, May 19, 2011 at 10:54 PM, Jacek <q.192.168.1.0_at_gmail.com> wrote:

> I tried "no mpls ip propagate-ttl forwarded" in MPLS lab but does not work
> exactly as described in some tutorials, including the following Cisco
> tutorial:
>
> http://www.cisco.com/en/US/tech/tk436/tk428/technologies_tech_note09186a008020a42a.shtml#mpls_tracerte
>
> When tracing from CE to CE I get a reply from latest MPLS router like in
> example below:
>
> R1--R2--R3--R4--R5
>
> R1 and R5 are CEs (no mpls configured)
> R2, R3, R4 are MPLS routers.
> R2 and R4 are configured with command "no mpls ip propagate-ttl"
>
> Trace from R1 to R5:
> R1#trace 10.1.45.5
> 1 10.1.12.2 8 msec 8 msec 4 msec
> 2 10.1.34.4 12 msec 44 msec 20 msec
> 3 10.1.45.5 24 msec 32 msec *
>
> According to the Cisco tutorial I should only get two replies, from R2 and
> R5. In my case I have also a reply from latest MPLS router (Line 2)
> Why ?
>
>
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Received on Fri May 20 2011 - 10:40:47 ART