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

[Saku Ytti]

On (2011-02-07 20:00 +0100), Peter Rathlev wrote:

> One might wish for selective TTL propagation, maybe using an access list
> of some kind. But since it has to be symmetric (AFAICT) it might not be
> easy at all. (I'm aware of the "local" exception when disable TTL

I've wanted the same for years. I don't see any technical problems in it,
just every hop in the MPLS network would need to have same ACL, which
determines to whom TTL is propagated.

On related note even before PFC3C was available I had TAC case open of
missing egress PE on traceroute. The problem is still there today, even
with PFC3C when disabling TTL propagation and using EXP null. I recently
reopened the case and DDTS CSCtn00835 is tracking the issue (i.e. it will
be fixed for EARL7.5, not sure yet in which releases).

> One of our last-mile providers recently disabled TTL propagation, and
> that has somewhat limited us when trouble shooting, so I do understand
> you point.

You could tell your core to pop when there is only 1 label, which should in
relatively typical scenarios translate to INET connections getting working
traceroute with interim latency visible and VPN/eVPN wouldn't.

-- 
  ++ytti