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High CPU utilization is seen on a Cisco Catalyst 4000 Supervisor that runs Cisco IOS software


Core issue

High CPU utilization is seen in a process that monitors the state of all line cards and ports. It is a low priority background task that runs when there is free CPU. In most cases, this process works fine and no issues are noticed.

Sometimes, based on how the review is scheduled to run in the system, the process can hit a software bug. The process then runs too frequently and uses all free CPU cycles. Once this condition occurs, the process does not recover, and constant high CPU is seen.

The output of the show platform health command shows that the RkiosPortMan Port Re process is using all of the free CPU.

This is a software defect. Refer to Cisco bug ID CSCeh08768 for more information.

In another scenario, it is also seen that after you enable the debug snmp packet command on the Supervisor Engine of a Catalyst 4000/4500 Switch, the CPU load of the Supervisor increases up to 100 percent.


This bug is fixed in Cisco IOS  Software Release 12.2(25)EWA2 and later versions.

As a workaround, either reboot the switch or upgrade to a release later than Cisco IOS Software Release 12.2(25)EWA which can be downloaded from Catalyst 4500/4000 Cisco IOS System Software.

In the case of CPU utilization due to a debug command, then it is normal to have high CPU utilization. If there exists a need to run debugs, then you should reduce the number of SNMP packets to the one strictly necessary, so that the impact on the CPU is minimized.

For more information, refer to the Understand the show platform health Command on the Catalyst 4500 Switches section of High CPU Utilization on Cisco IOS Software-Based Catalyst 4500 Switches for more information.