High CPU Usage on 3750

[SIMMN]

Hi,

I have this 3750 old switch running c3750-ipbase-mz.122-35.SE5.bin (I know it is old...) and it is used for connecting remote offices via 10Mbps circuits. It has been running fine for the last 12-month. But recently, I found the CPU usage is a little bit high, like in screenshot.

I know the average CPU usage is only about 10-20% but it bothers me that it constant has MAX CPU usage around 90+%...I also did show processes cpu sorted and the only thing having 3+% CPU usage is spanning tree...but that won't be enough to cause the CPU peaks... There is no special feature configure on the switch, just VLAN taggings.

Any suggestions on what to check?

[SIMMN]

I only have bufferred logging turned on but not much recorded there really...

[Leo Laohoo]

Upgrade your IOS to 12.2(55)SE9.

[SIMMN]

Frankly speaking, I have another 3750 (the same model) upgraded to the 12.2(55)SE9 but got similar symptom...plus that switch has nothing production plugged yet...

I start suspecting SNMP might cause the "issue"

[vincentbingli]

Hi,

To deal with transient cpu high issue, it's better to use EEM script to figure out the root cause. Only according to cpu history, it seems like something is polling your c3k every 30mins. Maybe it's snmp process.

EEM for your reference: http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/116141-trouble-eem-scripts-00.html

[jpl861]

Check SDM template if you are overloading the switch.

show sdm prefer
 The current template is "desktop routing" template.
 The selected template optimizes the resources in
 the switch to support this level of features for
 8 routed interfaces and 1024 VLANs.

  number of unicast mac addresses:                  3K
  number of IPv4 IGMP groups + multicast routes:    1K
  number of IPv4 unicast routes:                    11K
    number of directly-connected IPv4 hosts:        3K
    number of indirect IPv4 routes:                 8K
  number of IPv4 policy based routing aces:         0.5K
  number of IPv4/MAC qos aces:                      0.5K
  number of IPv4/MAC security aces:                 1K

If the numbers are good then you might want to check the entire LAN and causing temporary STP loops that would kick your CPU utilisation once in a while. Since you have mentioned that you are using this switch for WAN circuits, you may also check the show platform output.

show platform ip unicast failed route
Total of 0 covering fib entries

You should see zero or else that wouldn't be good.

[SIMMN]

Thanks, The SDM running is desktop default and I do not have routing enabled on switch.

[vasanthmanoharan]

still you have problem ?

then change logging level into informational and check any login session is hang in the switch.

[SIMMN]

I would not say "problem" but a concern.

The buffered logging level is debugging already...:)