Troubleshooting Cisco CPU Processor Overload

Below are some troubleshooting tips on Cisco CPU Processor Overload issues:

router# show proc cpu

Below are the major cpu processes on Cisco Switches / Router.

1. ARP Input Process: 
    This is arp messages the router is originating. 
    If have to do a lot of arp messages.

2. Net Background process: 
    Creates packet buffers. 
    when packets come in and hardware buffer is full, need this software buffers.
    If interface is getting overloaded, this cpu utilization process can go up.

3. IP Background Process: 
    Geared around handling config changes to interfaces. 
    If you Have a flapping interface for example, like the need to shutdown / reenable interface and interface modification.

4. TCP Timer Process: 
    This is responsible for handling TCP process handled by the router itself, not packets through the router.    Ex., ssh, telnet session to the router itself.

If above is suspected can check by or Fix by:

1. Default route pointed to an interface: point to a Default IP Address instead.

2. Interface throttles, overuns, ingores:  memory may not be enough to handle the traffic.

3. show tcp statistics / brief: for TCP Timer process.

• Show active TCP session TO, NOT THROUGH the router.  If see too high, may have a DDOS to your router.  Resolve by having an access-list to filter on the vty port.

4. show process cpu | exclude 0.00% or | history

Let me know if this helps.