[c-nsp] ios roulette blues (6500/7600 SXF)

[Phil Mayers]

Jon Lewis wrote:

> upgraded switch would not forward certain traffic.  It's similar to what 
> we used to occasionally see with 12.2S on the 7500 platform (dcef bugs [I 
> assume] where traffic between select src/dst IP pairs would not forward). 
> On the 7500, the solution that usually cleared it for us was ip cef (long 
> pause) ip cef dist.  On the 6509s, we don't have dcef.  We're seeing this 
> happen both for certain src/dst IPs inside of MPLS VPNs and in main table 
> IP routing.  In both the cases we've encountered, other src/dst pairs 
> traversing the exact same path through the network work.  Also the same 
> src/dst pairs are affected across reboots.
> 
> s72033-advipservicesk9_wan-mz.122-18.SXF8.bin apparently has the same 
> issue.  Rolling back to 122-18.SXD7 with no other config changes, we don't 
> see this issue.

I would open a TAC case. If it's very reproducible then, for a bug of 
this type, you will find TAC very responsive I suspect.

FYI we are running SXF6 and see no such problems.

You say it's certain source/dest pairs - not just certain destinations - 
which implies to me that whatever the fault is, it's unlikely to be 
plain old CEF.

Is this happening across multiple routers? If not, are there any common 
hardware components (linecards, groupings of certain ports) to the pairs 
which fail?

Are you using port-channels or ecmp layer3?

Are you running any netflow features (as opposed to just 
capture/export)? Microflow policing? QoS in general?

What does:

sh mls cef ip [vrf THEVRF] $THEIP det
sh ip cef [vrf THEVRF] $THEIP det

...report for one of the failing destinations? Ditto:

sh mls netflow ip destination THEIP detail module THEMOD
sh mls netflow ip source THEIP detail module THEMOD