SystemEXEC

show environment

Displays the environmental status of the chassis, including temperature, voltage, power supply, and fan information.

Overview

The 'show environment' command on Cisco NX-OS (Nexus) provides a comprehensive view of the physical health of the switch chassis. It reports on four key subsystems: fans, power supplies, temperature sensors, and voltage regulators. This command is essential for proactive hardware monitoring and troubleshooting environmental issues that could lead to device failure or performance degradation. In a data center environment, Nexus switches are critical infrastructure; any environmental anomaly can cause service disruption. The command is executed in EXEC mode and requires no special privileges. It is non-disruptive and can be run at any time. The output is organized by subsystem, making it easy to scan for problems. For example, a power supply showing 'FAIL' indicates a hardware fault that needs immediate replacement. Temperature readings above threshold trigger warning or critical alerts, which may cause the switch to shut down to prevent damage. Voltage readings outside normal range can indicate failing components. This command fits into troubleshooting workflows as a first step when investigating unexpected reboots, performance issues, or hardware alarms. It is also used during routine maintenance to verify that all components are operating within specifications. On NX-OS, the command supports optional keywords to filter output: 'all' shows everything, 'fan' shows only fan status, 'power' shows power supply details, 'temperature' shows thermal readings, and 'voltage' shows voltage levels. This granularity allows engineers to focus on specific subsystems without wading through irrelevant data. Understanding the output is crucial for CCNP Data Center candidates, as environmental monitoring is a key topic in the exam blueprint.

Syntax·EXEC

show environment [all | fan | power | temperature | voltage]

When to Use This Command

Check if any power supply has failed or is in a warning state.
Monitor temperature sensors to prevent overheating and potential shutdown.
Verify fan tray operation and RPM values during maintenance.
Troubleshoot unexpected device reboots by examining voltage readings.

Parameters

Parameter	Syntax	Required	Description
all	show environment all	Optional	Displays all environmental information including fan, power, temperature, and voltage. This is the default behavior if no keyword is specified.
fan	show environment fan	Optional	Displays only the fan status, including fan tray presence and RPM if available. Useful for quick fan health checks.
power	show environment power	Optional	Shows detailed power supply information including model, status, input/output specifications, and serial numbers. Essential for power redundancy verification.
temperature	show environment temperature	Optional	Displays temperature readings for each module with status (OK, WARNING, CRITICAL). Helps identify overheating components.
voltage	show environment voltage	Optional	Shows voltage levels for each module with status. Voltage deviations can indicate failing hardware.

Command Examples

Basic environment status

show environment

Environmental Status
-------------------
Fan:
1  N/A  N/A  N/A
2  N/A  N/A  N/A
3  N/A  N/A  N/A

Power Supply:
Voltage: 12.00 V
Power Supply 1 (PS1): 1100 W, Status: OK
Power Supply 2 (PS2): 1100 W, Status: OK

Temperature:
Module 1: 45 C, Status: OK
Module 2: 42 C, Status: OK

Voltage:
Module 1: 1.2 V, Status: OK
Module 2: 1.2 V, Status: OK

Shows overall environment: fan status (N/A if not present), power supply wattage and status, temperature per module in Celsius, and voltage per module. 'OK' indicates normal operation.

Detailed power supply information

show environment power

Power Supply: PS1
Model: N9K-PAC-1100W
Status: OK
Input: 100-240V AC
Output: 12V DC, 1100W
Serial: XYZ1234567

Power Supply: PS2
Model: N9K-PAC-1100W
Status: FAIL
Input: 100-240V AC
Output: 12V DC, 1100W
Serial: ABC9876543

Lists each power supply with model, status (OK or FAIL), input/output specs, and serial number. A FAIL status indicates the supply is not providing power.

Temperature sensors detail

show environment temperature

Module 1: Temperature 45 C, Status: OK
Module 2: Temperature 42 C, Status: OK
Module 3: Temperature 48 C, Status: WARNING
Module 4: Temperature 55 C, Status: CRITICAL

Displays temperature per module. OK is normal, WARNING indicates approaching threshold, CRITICAL means immediate action needed to avoid shutdown.

Understanding the Output

The 'show environment' command output is divided into sections: Fan, Power Supply, Temperature, and Voltage. Each section lists components with their status. For fans, 'N/A' means no fan is installed or detected. Power supply status shows 'OK' for normal operation, 'FAIL' for failure, or 'WARNING' for marginal conditions. Temperature is shown in Celsius with status: 'OK' (normal), 'WARNING' (approaching threshold), or 'CRITICAL' (exceeded threshold). Voltage readings are per module with status similar to temperature. Healthy values: temperature below 50°C, voltage within ±5% of nominal, power supply status OK. Problem values: temperature above 60°C, voltage deviations >10%, power supply FAIL or WARNING. The command helps quickly identify hardware issues that could lead to downtime.

Configuration Scenarios

Monitoring Power Supply Redundancy

A data center Nexus 9000 switch has two power supplies for redundancy. One supply fails, and you need to verify the status.

Topology

Nexus 9000 with PS1 and PS2

Steps

1.Connect to the switch via SSH or console.
2.Enter EXEC mode.
3.Execute 'show environment power' to check power supply status.
4.Interpret output: if one supply shows FAIL, plan for replacement.

Configuration

! No configuration needed; this is a show command.

Verify: After replacing the failed supply, run 'show environment power' again to confirm both show OK.

Watch out: If the switch is running on a single supply, the status may show OK but the system is non-redundant. Always check both supplies.

Responding to Temperature Warning

A Nexus switch reports a temperature warning on module 3. You need to investigate and take corrective action.

Topology

Nexus 9000 with multiple line cards

Steps

1.Run 'show environment temperature' to see all module temperatures.
2.Identify the module with WARNING or CRITICAL status.
3.Check ambient temperature and airflow; ensure fans are working with 'show environment fan'.
4.If necessary, clean air filters or relocate the switch to a cooler area.

Configuration

! No configuration change; environmental monitoring is automatic.

Verify: Re-run 'show environment temperature' after corrective actions to confirm status returns to OK.

Watch out: A WARNING status may escalate to CRITICAL if ignored; the switch may shut down to protect hardware.

Troubleshooting with This Command

When troubleshooting environmental issues on Cisco NX-OS (Nexus), the 'show environment' command is your first line of defense. Start with the basic command to get an overview. If you see any status other than OK, investigate further using the specific keywords. For example, if a power supply shows FAIL, immediately check if the switch is running on a single supply. Use 'show environment power' to get details like model and serial number for replacement. If temperature is high, use 'show environment temperature' to pinpoint the hot module. Check fan status with 'show environment fan' to ensure cooling is adequate. Voltage warnings often accompany other issues; use 'show environment voltage' to see if any module is out of range. In a troubleshooting workflow, correlate environmental issues with syslog messages. For instance, a 'POWER-1-POWER_FAILURE' message aligns with a failed power supply. Also, check 'show logging last 10' for recent events. If the switch has rebooted unexpectedly, environmental causes like overheating or power loss are common. Always verify power redundancy: if one supply fails, the switch should continue operating, but it's a critical condition. For temperature, ensure the ambient temperature is within specifications (typically 0-40°C). If fans are not spinning, check for obstructions or fan tray failure. On Nexus platforms, some modules have individual temperature sensors; a single sensor in warning may not indicate a systemic issue, but it should be investigated. Use 'show environment all' for a comprehensive dump when opening a TAC case. Remember that environmental monitoring is passive; the switch does not automatically fix issues. You must take corrective action based on the output. In high-availability environments, having spare power supplies and fan trays on site is recommended. For persistent issues, consider upgrading firmware as newer versions may improve sensor accuracy or thresholds.

CCNA Exam Tips

Remember that 'show environment' is a non-disruptive command used for monitoring hardware health.

On NX-OS, the output includes module-level granularity; be prepared to interpret per-module status.

Know that temperature thresholds vary by platform; typical warning is around 50°C, critical at 60°C.

In exams, you may be asked to identify a failing power supply from the output.

Common Mistakes

Assuming all fans are present; 'N/A' means not installed, not failed.

Ignoring WARNING status; it indicates a potential problem that should be investigated.

Confusing voltage readings with power supply output; voltage is per module, power supply shows wattage.

Platform Notes

On Cisco NX-OS (Nexus), the 'show environment' command is similar to Cisco IOS but with more granularity per module. In IOS, the command often shows a single temperature for the entire chassis, while NX-OS breaks it down per module (e.g., line card, supervisor). The power supply output in NX-OS includes model and serial numbers, which is useful for inventory. The fan section in NX-OS may show 'N/A' for empty slots, whereas IOS might omit them. Voltage monitoring is more detailed in NX-OS, showing per-module voltages. Equivalent commands on other platforms: on Juniper Junos, use 'show chassis environment' or 'show chassis hardware'; on Arista EOS, use 'show system environment'. On Cisco IOS-XR, the command is 'show environment' but output format differs. NX-OS also supports 'show environment power detail' for extended power supply info. Version differences: older NX-OS versions may not support the 'all' keyword; use the base command instead. On Nexus 9000 series, the command also shows fabric module temperatures if present. Always refer to the specific platform documentation for exact thresholds, as they vary by model.

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