[c-nsp] TTL not decrementing (MPLS, SXI, Sup720)

[Daniel Dib]

On må, feb 07, 2011 at 15:16:30, Peter Rathlev wrote:
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] TTL not decrementing (MPLS, SXI, Sup720)
> 
> Hi Manu,
> 
> On Mon, 2011-02-07 at 15:09 +0100, Manu Chao wrote:
> > If IP TTL propagation is disabled in your MPLS Core with the no mpls 
> > ip propagate-ttl command in global configuration mode, the TTL value 
> > is not copied in the IP header and on your end to end traceroute.
> 
> So you're saying it works as expected with "no mpls ip propagate-ttl"?
> That would be interesting.
> 
> We currently use TTL propagation and we like it from a trouble 
> shooting perspective. But we're also getting tired of people not able 
> to interpret traceroutes, so we've thought about disabling it anyway.
> 
> We've actually had a request where the users wanted us to "create a 
> more direct route" because they saw "too many" hops in their 
> traceroute. And I bet they're not willing to pay for a new stretch of 
> glass...
> 
> --
> Peter

You could disable it for forwarded packets and keep it for local packets for
troubleshooting. Use no mpls ip propagate-ttl forwarded. This would let you
do traceroutes from the devices but NMS stations etc would be affected which
could be a disadvantage.

/Daniel