help! 6500 doing weird stuff

Unanswered Question
Sep 20th, 2009
User Badges:

Hey Guys,

My Cat 6500 is acting strange, the "ip input" processes is running the CPU to over 50% which is causing issues on my network. Does this mean that the IP packets are not being processed at layer 2? Has anyone seen this?

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Giuseppe Larosa Mon, 09/21/2009 - 01:16
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

Hello Brent,

>> the "ip input" processes is running the CPU to over 50%

this means that a big quota of traffic is process switched = sent to main cpu instead of being CEF switched.

You need to understand why this is happening.

For example other collegues have reported very high cpu after having enabled DHCP snooping.

Also check if you have any SPAN sessions.

we have seen that if a SPAN session is trying to push more traffic then what the destination port can support ( for example 3 Gbps towards a 1 GE destination port) when oversubscription is high cpu can reach 100%.


CSCsi74194 Bug Details

Egress SPAN may cause high CPU

see for troubleshooting high cpu on C6500


Hope to help


Brent Rockburn Mon, 09/21/2009 - 06:52
User Badges:

Thanks Giuseppe,

Turns out I found a routing loop on my network ... spt failed open as is it's default and BOOM!!! Broadcast storm .. so I physically killed the redundant link to my cat and voila spt found it's feet again.

Thanks for the info.


This Discussion