show environment
Displays the environmental status of the device, including temperature, voltage, and fan status, to monitor hardware health and detect potential failures.
show environmentWhen to Use This Command
- Checking system temperature after a cooling fan failure alert
- Verifying power supply voltage during a site power audit
- Monitoring fan speed before scheduled maintenance to ensure proper cooling
- Troubleshooting unexpected shutdowns by reviewing environmental history
Command Examples
Basic show environment output
show environmentEnvironmental Status -- System Temperature -- Temperature: 45 Celsius Temperature Threshold: 65 Celsius -- Power Supply -- Power Supply 1: Normal Power Supply 2: Normal -- Fan Status -- Fan 1: Normal Fan 2: Normal Fan 3: Normal -- Voltage -- +5V: 5.00 V +12V: 12.10 V -12V: -12.00 V
Line 1: Header. Line 2-4: System temperature is 45°C, below the threshold of 65°C (safe). Line 6-8: Both power supplies are operating normally. Line 10-13: All three fans are normal. Line 15-18: Voltages are within expected ranges (5V, 12V, -12V).
show environment all (detailed)
show environment allEnvironmental Status -- System Temperature -- Temperature: 50 Celsius Temperature Threshold: 65 Celsius -- Power Supply -- Power Supply 1: Normal Power Supply 2: Failed -- Fan Status -- Fan 1: Normal Fan 2: Normal Fan 3: Failed -- Voltage -- +5V: 4.95 V +12V: 11.80 V -12V: -11.90 V -- History -- Last Power Supply Failure: 10:30:00 UTC Mon Mar 15 2023 Last Fan Failure: 10:25:00 UTC Mon Mar 15 2023
Shows more detail including history. Temperature is 50°C (still safe). Power Supply 2 has failed (critical). Fan 3 has failed (critical). Voltages are slightly low but within tolerance. History shows recent failures at specific times.
Understanding the Output
The 'show environment' command provides a snapshot of the device's physical health. The 'System Temperature' field shows the current internal temperature in Celsius and the threshold at which an alarm triggers. Normal operating temperature is typically below 60°C; values near the threshold indicate cooling issues. 'Power Supply' shows each PSU status: 'Normal' means operational, 'Failed' means no output, and 'Absent' means not installed. 'Fan Status' lists each fan; 'Normal' is good, 'Failed' means the fan is not spinning. 'Voltage' displays key rails; acceptable ranges are usually ±5% of nominal (e.g., +5V should be 4.75-5.25V). If any value is out of range, immediate investigation is needed. The 'all' variant adds a history section showing timestamps of recent failures, useful for trend analysis.
CCNA Exam Tips
CCNA exam may ask which command to use to check if a fan has failed — answer: 'show environment'
Be aware that 'show environment' is a Privileged EXEC command, not available in User EXEC mode
The exam might present an output with a failed power supply and ask what action to take — replace the PSU
Know that temperature thresholds vary by platform; always compare to the specific device's threshold
Common Mistakes
Mistake 1: Using 'show environment' in User EXEC mode — it will not work; must be in Privileged EXEC
Mistake 2: Ignoring a 'Failed' fan status because the device still runs — can lead to overheating and shutdown
Mistake 3: Confusing 'show environment' with 'show env' (which is not a valid Cisco IOS command)
Related Commands
show inventory
Displays the hardware inventory of the device, including serial numbers and part numbers for all installed modules, used for asset management and verifying hardware components.
show logging
Displays the state of system logging (syslog) on the device, including buffer contents, logging configuration, and statistics, used for troubleshooting and monitoring system events.
show version
Displays system hardware and software information, including IOS version, uptime, memory, interfaces, and configuration register, used to verify device identity and software compatibility.
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