Troubleshooting 101

Troubleshooting CPU

R# show process cpu [sorted COLUMN]
CPU utilization for five seconds: 6%/3%; one minute: 7%; five minutes: 7%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
115 16866996 43153481 490 0.72% 0.52% 0.52% 0 Skinny Msg Serve
163 88084 1683463169 0 0.38% 0.43% 0.41% 0 HQF Shaper Backg
129 26750192 94979172 281 0.38% 0.37% 0.33% 0 IP Input
In this example the 5 seconds CPU utilziation is 6%/3% with the first percentage representing total CPU utilization and the second percentage representing interrupt utilization. Interrupt utilization is time spent by the CPU dealing with network packets (data plane). The difference between the 2 numbers is the ammount of time spent by the CPU on dealing with the other processes of the device. An interrupt percentage between 5-10% is acceptable. CPU spikes aren't neceserily bad but constantly keeping a high CPU utilization is a cause of concern.

Troubleshooting memory

R# show memory
Head Total(b) Used(b) Free(b) Lowest(b) Largest(b)
Processor 47C407A0 920385632 107682552 812703080 802714184 799891248
I/O 3EA00000 23068672 22344664 724008 602976 82844
Processor memory
Address Bytes Prev Next Ref PrevF NextF Alloc PC what
47C407A0 0000000932 00000000 47C40B74 001 ------ ------ 40390618 *Packet Header*
47C40B74 0000000932 47C407A0 47C40F48 001 ------ ------ 40390618 *Packet Header*
47C40F48 0000000932 47C40B74 47C4131C 001 ------ ------ 40390618 *Packet Header*
I/O memory is the memory used for temporary packet buffering. A device with low free memory can become slow or even reboot.

Troubleshooting interfaces

R# show interface [INTF-ID]
R# show controllers [INTF-IF]
When troubleshooting interfaces, look for:
  • MTU
  • input queue drops - signify that the traffic is dropping because the router is receiving more traffic than it can handle
  • Output queue drops - these are usuaully a result of congested links
  • Input errors - these may be result of interface problems, duplex errors, CRC errors
  • Output errors - these are usually the result of duplex issues
show controllers command providdes interface hardware statistics and may show different info based on controller type.

Other troubleshooting commands

R# show platform
! Can be helpful when troubleshooting a router reload