[c-nsp] Output buffer errors

[Holemans Wim]

Last week we replaced one of our 6500's (including FWSM) and since then
we are seeing
output errors on a 3550 router that is a few switches away from the
router.

Schema:
 provider--- 3550  --- 2970 --- IPS --- 2970 --- FWSM/6506-E -- internal
network
         ^   access
         |    router
       output errors on this link.

This is the error message on the 3550 external port.

     1150 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     1150 output buffer failures, 0 output buffers swapped out

What we did : we replaced a 6509/sup2, FWSM 2.1 with a 6506-E/sup32,
FWSM 3.1
The vlan that connects the 3550 and 6506 internally, ends on the FWSM. 
On the 2970 switches we don't see any errors. After the swap the output 
errors appeared on the external link. Connections between 6506, 2970,
IPS, 2970
are 2Gig channels but load on each of the Gig links never goes above 150
Mbit.
External connection is a 1 Gig link. 

We don't have a clue where these errors come from. Load on the links is
still
the same as before. Anyone who has a clue on where these errors come
from ?
Any suggestion on how to 'debug' this ? 
(please no discussion on position of IPS. It is there for some reasons I
won't
explain here).

Thanks,


Wim Holemans
Network Services
University of Antwerp