we have a problem with our Core-Routers: Cat 6506 with Sup 720, Running on s72033-advipservicesk9_wan-mz.122-18.SXF15a:
If we ping the router, ca. 5% of all Packets have long responsetimes or even timeouts. On SSH-Sessions to the router, we have some DUP ACKs.
But: The traffic, which goes through those Routers is not delayed at all. If we ping a Switch or Server behind the Router, Response times are <= 1ms. SSH-Sessions on simple Cat-3560-Switches behind the core have no DUP ACKs. Only traffic to the Cat 6506 itself has problems...
- CPU is constant on 5-10%.
- 'Normal' Traffic does not care wether it is switched, routed between vlans or router between p2p-routed links, it never gets hurt.
- It does not matter, which Interface we address on the router. If we ping more than one adress on the same router, every Interface times out at the same time.
- The Sup32 - Cat 6506 in our Server Access (running s3223-advipservicesk9_wan-mz.122-18.SXF15a, Switching only) do not have time outs and DUP ACKs, although they sometimes have Response Times > 10 ms. Currently, we do not include them into our troubleshooting...
- No entries in logging level debugging.
- Downgrading to 122-18.SXF12 did not change anything.
- The more Traffic the router has, the more Timeouts occur. One Router, which has no Vlans on HSRP active or Spanning Tree Root, has no Timeouts at all and only very few Response Times > 10ms.
As normal traffic seems not to be affected, this is not a catastrophe, but we don't like the smell in our noses.
Does anybody have any idea, where we should continue our diagnosis, we are sorta shot out...
thx in advance and greeting from switzerland