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New Member

C6500 CPU 90% with DHCP

Dear All

we have this situation in our network where whenever we have a power shutdown due to maintenance its takes the C6500 core CPU to reach 90% and takes almost an hour or more to settle down.

we have DHCP server configured on it for almost 3000 devices, so i suspect DHCP request broadcast flooding, the console hangs and nothing can be accessed.

Thus we started to shut all uplink ports and get them UP 2-3 ports at a time which takes 1-2 hrs to get network operational.

we have had a crash before, trying to decode it...

Client seems to be confused as for him its the SUP720 which is the best and should not get impacted.

thinking of dividing the dhcp services on both cores !!

any technical justification will be highly appreciated.



Cisco Employee

Re: C6500 CPU 90% with DHCP

Its very possible its the DHCP but I am surprised your console port does not respond for an hour during the problem.

IOS switches can act as DHCP servers but its done in software. If you have an enterprise network as large as yours(3000 hosts), I would say you should invest in couple windows DHCP server.

New Member

Re: C6500 CPU 90% with DHCP

Thanks mate for the info, I'm sure it getting processed switched by C6500 that's why the issue.


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