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Monitoring Commands

The commands worth running periodically to catch problems before they become visible symptoms, plus the ones to reach for once something already looks wrong.

All commands on this page are Cisco IOS, run from privileged EXEC (Switch#).

System Health

! CPU utilization, and which process is consuming it
show processes cpu
! Same, sorted by usage — fastest way to spot a runaway process
show processes cpu sorted
! Memory usage and free space
show memory statistics
! Temperature, fan, power supply status (where supported)
show env all

A switch quietly running hot or low on memory rarely fails outright mid-check — it fails later, under load. Check these in advance, not just when something's already broken.

Interface Health

Covered in more depth in Interface Management:

! Quick per-port summary
show interfaces status
! Error counts across all interfaces at a glance
show interfaces counters errors
! Focused check on a specific port
show interfaces Gi0/1 | include error|drop

Logging & Traps

! Recent local log messages — see Syslog
show logging | include %
! SNMP engine status — see SNMP
show snmp

Routing / Connectivity

! Confirm the routing table looks as expected — see Routing
show ip route
! Up/down status and IP assignment across all interfaces
show ip interface brief
! Basic reachability check
ping <gateway>

Getting a Full Snapshot

When something's wrong and you need to hand off details (to a colleague, or for a support case), show tech-support bundles a large set of diagnostic output into one capture:

show tech-support

This output is long — redirect it to a file rather than reading it live on a console session (use the output modifier — show tech-support | redirect flash:showtech.txt, or | tee flash:showtech.txt to watch it scroll while saving — or capture it with your terminal emulator's session logging; there is no copy form for show output).