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Updated:December 2, 2022
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This document describes how to collect CPU utilization on Cisco IOS® devices that use Simple Network Management Protocol (SNMP).
There are no specific requirements for this document.
The information in this document is only for devices that run Cisco IOS software. The c7500 example with multiple CPUs uses Cisco IOS Software Release 12.0(22)S3.
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.
Critical router functions, like routing protocol processing and process packet switching, are handled in memory and share the CPU. Thus, if CPU utilization is very high, it is possible that a routing update cannot be handled, or a process-switching packet is dropped. From the CISCO-PROCESS-MIB , the cpmCPUTotal5minRev MIB object value reports the percentage of the processor in use over a five-minute average.
The cpmCPUTotal5minRev MIB object provides a more accurate view of the performance of the router over time than the MIB objects cpmCPUTotal1minRev and cpmCPUTotal5secRev . These MIB objects are not accurate because they look at CPU at one minute and five second intervals, respectively. These MIBs enable you to monitor the trends and plan the capacity of your network. The recommended baseline rising threshold for cpmCPUTotal5minRev is 90 percent. Based on the platform, some routers that run at 90 percent, for example, 2500s, can exhibit performance degradation versus a high-end router, for example, the 7500 series, which can operate fine.
cpmCPUTotal5secRev(.184.108.40.206.220.127.116.11.18.104.22.168.1.6): The overall CPU busy percentage in the last five-second period. This object deprecates the object cpmCPUTotal5sec and increases the value range to (0..100).
cpmCPUTotal1minRev(.22.214.171.124.126.96.36.199.188.8.131.52.1.7): The overall CPU busy percentage in the last one-minute period. This object deprecates the object cpmCPUTotal1min and increases the value range to (0..100).
cpmCPUTotal5minRev(.184.108.40.206.220.127.116.11.18.104.22.168.1.8): The overall CPU busy percentage in the last five-minute period. This object deprecates the object cpmCPUTotal5min and increases the value range to (0..100).
This table shows the new MIBs and their objects beside the old MIBs and objects they replace:
Cisco IOS Software releases 12.2(3.5) or later
Cisco IOS Software releases later to 12.0(3)T and prior to 12.2(3.5)
The percentage of CPU time at interrupt level (fast-switched packets), over a five-second period. If you take the difference between the first and second, you arrive at the five-second percentage the router spends at the process level. In this case, the router spends one percent at the process level over the last five seconds (process- switched packets - No MIB variable).
The CPU utilization over the last minute [also available through the object avgBusy1 (.22.214.171.124.126.96.36.199.1.57)]
When you poll CPU utilization variables and any other SNMP variables, the actual CPU utilization is affected. Sometimes, the utilization is 99 percent when you continuously poll the variable at one-second intervals. It is an overkill to poll so frequently but take into consideration the impact to CPU when you determine how frequently you want to poll the variable.
This implies that the Cisco IOS device must support bothCISCO-PROCESS-MIBandENTITY-MIBfor you to be able to retrieve relevant information about CPU utilization. The only case where you do not need to have or useENTITY-MIBis when you only have a single CPU.
Monitor the use of multiple CPUs in the 7500 chassis (RSP and two VIPs). The same applies to GSR linecards. Use Cisco IOS Software Release 12.0(22)S3 or later when you poll c7500 or GSR for these values. Be aware of the related bugs: Cisco bug ID CSCdw52978 and Cisco bug ID CSCdp17238.
Note: Only registered Cisco users have access to internal Cisco bug information and Cisco tools.
Poll cpmCPUTotal5min (.188.8.131.52.184.108.40.206.220.127.116.11.1.5)to get "overall CPU busy percentage in the last 5 minute period" for all CPUs in the chassis. The output shows that the 7507 device has three CPUs, utilized for 10%, 1%, and 2% during last 5 minutes.
In order to identify the particular card to which each physical entry is related, poll correspondent entPhysicalName (.18.104.22.168.22.214.171.124.126.96.36.199)entry, with the exact indexes 9, 25, 28 from Step 2, as a last digit. You see that RSP is utilized for 10%, and VIPs in slots 4 and 6 are utilized for one and two percent.