[c-nsp] Label still appearing in traceroute after disabling ttl propagation

Jared Mauch jared at puck.nether.net
Tue Jul 30 13:43:09 EDT 2013


Disable TTL != don't copy label into ICMP TTL Expired message.

- Jared

On Jul 30, 2013, at 1:37 PM, John Neiberger <jneiberger at gmail.com> wrote:

> I think either we're just doing something wrong or perhaps we're running
> into a bug. I did find this one, which sounds similar:
> 
> https://tools.cisco.com/bugsearch/bug/CSCtd17126
> 
> I'm not sure if that is fixed in 4.1.0 or not.
> 
> 
> On Tue, Jul 30, 2013 at 11:01 AM, John Neiberger <jneiberger at gmail.com>wrote:
> 
>> W
>> e're running into an interesting problem. We have a simple lab setup like
>> this:
>> 
>> CE1 -- PE1 --- P1 --- P2 --- PE2 --- CE2
>> 
>> We have "mpls ip-ttl-propagate disable" on all PE and P routers, but if we
>> trace from CE1 to CE2, we still see an MPLS label coming from the PE2
>> router. If we trace CE2 to CE1, we see a label on the hop from P1 to PE1.
>> 
>> If we have ttl propagation completely disabled, why would we still see the
>> label and P-to-PE link in the path?
>> 
>> All P and PE routers are IOS XR running 4.1.0.
>> 
>> Thanks,
>> John
>> 
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