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Increase in CPU utilization after upgrade

We have upgraded 19 switches with configurations to support a pending rollout of Telephony over IP (ToIP). At present, there are no phones connected to the switches yet, so no additional voice traffic or load associated with ToIP is being produced.

However, I have noticed that once the switches are upgraded, we see an increase in processor utilisation on 2950 & 3500 switches, with the 3500?s (WS-C3548-XL-EN) showing the worst increase. Prior to upgrade, without any active users, the 3500?s would run at around 50% processor utilisation (55% with load). Following the upgrade, without any load this figure has risen to 75%, and with load is around 80%. During start of day activities this morning (PC startup / DHCP address allocation / user login etc), one switch became so unresponsive that our monitoring console reported it was unreachable. When I connected, I noted the processor utilisation was 85% ? 87%.

No physical cabling changes have been carried out, only the IOS has been upgraded & the new ToIP configs have been deployed. The ToIP changes include :

TACACS authentication

Re-sized (smaller) VLANs & creation of ToIP-specific VLAN

Trunking of Voice & Data VLANs to FastEthernet ports

Previous IOS Version : IOS (tm) C3500XL Software (C3500XL-C3H2S-M), Version 12.0(5)WC10, RELEASE SOFTWARE (fc1)

New IOS Version : IOS (tm) C3500XL Software (C3500XL-C3H2S-M), Version 12.0(5)WC16, RELEASE SOFTWARE (fc1)


Re: Increase in CPU utilization after upgrade

Actually the 3500Xl are know to be having this problem and their CPU utilization does range normally between 50-80%. Here is the document

I have one of my customers running these switches and they run usually in 50 - 70%. No choice here mate. I think if your earlier image worked well your option would be to downgrade.