DiagnosticsEXEC

show tech-support

Collects a comprehensive set of system information for troubleshooting and technical support.

Overview

The show tech-support command is a powerful diagnostic tool on Cisco NX-OS (Nexus) that aggregates a wide range of system information into a single output. It is designed to provide a comprehensive snapshot of the device's operational state, configuration, and historical logs, making it indispensable for troubleshooting and technical support. The command collects data from numerous subsystems, including hardware inventory, software version, running configuration, interface status, routing tables, VLAN information, spanning-tree topology, neighbor discovery protocols (CDP/LLDP), system logs, and more. This consolidated output helps engineers quickly identify anomalies, misconfigurations, or hardware failures without manually running dozens of individual commands.

On Cisco NX-OS, show tech-support is particularly valuable due to the complexity of data center environments where Nexus switches operate. It is often the first command requested by Cisco TAC when opening a support case, as it provides all necessary context for remote diagnosis. The command can be executed in EXEC mode and supports options to focus on specific features (e.g., show tech-support feature ospf) or sections (e.g., show tech-support section interface), reducing output size for targeted analysis. Additionally, the output can be redirected to a file using the 'file' parameter, which is essential for preserving the data for later review or sharing.

In troubleshooting workflows, show tech-support is typically run after a problem is observed, such as a network outage, performance degradation, or unexpected reboot. The output helps correlate events by providing timestamps from logs and uptime information. For example, if an interface flapped, the logs section will show the flap events, and the interface section will confirm the current status. The command also captures core dumps or crash information if available, aiding in root cause analysis. However, due to its comprehensive nature, it can be resource-intensive and may take several minutes to complete on large chassis; therefore, it should be used judiciously in production environments.

Syntax·EXEC

show tech-support [detail | {feature <feature-name>} | {section <section-name>} | {file <filename>} | {no-more}]

When to Use This Command

Gathering all system logs, configurations, and diagnostics before opening a TAC case.
Capturing a snapshot of the system state after a crash or unexpected reboot.
Collecting specific feature-related data (e.g., OSPF, BGP) for targeted troubleshooting.
Saving the output to a file for offline analysis or sharing with support engineers.

Parameters

Parameter	Syntax	Required	Description
detail	detail	Optional	Provides more detailed output, including additional debug-level information. Use when deeper analysis is needed, but be aware it increases output size significantly.
feature	feature <feature-name>	Optional	Limits the collection to a specific feature, such as ospf, bgp, or vpc. This reduces output and focuses on relevant data for targeted troubleshooting.
section	section <section-name>	Optional	Collects only a specific section of the tech-support output, like interface or logging. Useful for quickly retrieving a subset of data without the full dump.
file	file <filename>	Optional	Saves the output to a file in the specified filesystem (e.g., bootflash:). This is recommended for large outputs to avoid terminal buffer overflow and for sharing with support.
no-more	no-more	Optional	Disables the paging (more) prompt, allowing the entire output to scroll without user intervention. Useful when capturing output to a terminal log or file.

Command Examples

Basic tech-support collection

show tech-support

--- show tech-support ---
Time: Mon Mar 10 14:23:45 2025

--- show version ---
Cisco Nexus 9000 C93180YC-FX3
Software
  BIOS: version 07.70
  NXOS: version 9.3(10)
  BIOS compile time: 12/09/2024
  NXOS image file is: bootflash:///nxos.9.3.10.bin
  NXOS compile time: 1/10/2025 10:00:00 [01/10/2025 14:00:00]

Hardware
  cisco Nexus 9000 C93180YC-FX3 Chassis
  Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz with 16400924 kB of memory.
  Processor Board ID FOC12345678

  Device name: N9K-1
  bootflash: 53298520 kB

Kernel uptime is 45 day(s), 12 hour(s), 30 minute(s), 15 second(s)

Last reset at 123456 usecs after  Mon Mar 10 14:23:45 2025
  Reason: Reset Requested by CLI command reload
  System version: 9.3(10)
  Service: 

plugin
  Core Plugin, Ethernet Plugin

--- show running-config ---
!Command: show running-config
!Running configuration last done at: Mon Mar 10 14:20:00 2025
!Time: Mon Mar 10 14:23:45 2025

version 9.3(10)
hostname N9K-1
...

--- show logging ---
2025 Mar 10 14:20:01 N9K-1 %$ VDC-1 %$ %USER-0-SYSTEM_MSG: show tech-support initiated
...

--- show interface brief ---
Ethernet      VLAN    Type Mode   Status  Reason                   Speed     Port
Interface                                                                    Ch
Eth1/1        1       eth  routed up      none                      10000(D) --
Eth1/2        1       eth  routed up      none                      10000(D) --
...

--- show ip route ---
IP Route Table for VRF "default"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]

10.1.1.0/24, ubest/mbest: 1/0
    *via 10.1.1.1, Eth1/1, [110/41], 1d02h, ospf-1, intra
...

--- End of show tech-support ---

The output begins with a timestamp and then sequentially displays the output of multiple show commands: show version (system hardware/software info), show running-config (current configuration), show logging (system logs), show interface brief (interface status), show ip route (routing table), and many more. Each section is clearly labeled. The output ends with a marker.

Save tech-support to a file

show tech-support file bootflash:techsupport-03102025.txt

Building configuration ...
Tech-support file saved to bootflash:techsupport-03102025.txt

The command saves the tech-support output directly to a file in bootflash. The confirmation message indicates the file was created successfully.

Understanding the Output

The show tech-support output is a concatenation of many individual show commands, each prefixed with a header like '--- show <command> ---'. The first section is typically 'show version', which provides hardware model, NX-OS version, uptime, and last reset reason. This is crucial for identifying the platform and software level. Next, 'show running-config' displays the entire configuration, which is essential for verifying settings. The 'show logging' section shows system messages, including errors or warnings. Interface status is shown via 'show interface brief', where 'up' indicates operational, 'down' indicates a problem. Routing tables from 'show ip route' reveal reachability and routing protocol details. Other sections include 'show vlan', 'show spanning-tree', 'show cdp neighbors', etc. Healthy output shows interfaces up, routes present, and no critical errors. Problematic output may show interfaces down, missing routes, or repeated error logs. The output is large; use the 'no-more' option to avoid paging or save to a file for analysis.

Configuration Scenarios

Collecting tech-support for OSPF issue

A Nexus switch is experiencing OSPF neighbor flapping. The engineer needs to gather OSPF-specific data without the full tech-support dump.

Topology

N9K-1 --- N9K-2 (OSPF area 0)

Steps

1.Connect to the Nexus switch via SSH or console.
2.Enter EXEC mode (enable).
3.Run the command: show tech-support feature ospf file bootflash:ospf-tech.txt
4.Transfer the file to a remote server for analysis.

Configuration

! No configuration change needed; this is a diagnostic command.

Verify: Check the file size and contents using 'dir bootflash:ospf-tech.txt' and 'more bootflash:ospf-tech.txt'.

Watch out: Ensure the feature name is correct (e.g., 'ospf' not 'OSPF'); the command is case-insensitive but must match the feature name as shown in 'show tech-support ?'.

Saving full tech-support for TAC

A Nexus 9000 switch experienced a crash. The engineer needs to collect all data for Cisco TAC.

Topology

Single Nexus 9000 chassis

Steps

1.After the switch reloads, log in and enter EXEC mode.
2.Run: show tech-support file bootflash:crash-$(date +%Y%m%d-%H%M%S).txt
3.Copy the file to a TFTP/SCP server using 'copy bootflash:crash-... tftp://...'.
4.Open a TAC case and provide the file.

Configuration

! No configuration change.

Verify: Verify the file exists and has substantial size (typically >1MB).

Watch out: The command may take a long time on a large chassis; plan accordingly. Use 'no-more' if running interactively to avoid paging.

Troubleshooting with This Command

The show tech-support command is a cornerstone of troubleshooting on Cisco NX-OS. When a network issue arises, the first step is often to run this command to capture a baseline of the system state. The output is structured into sections, each corresponding to a specific show command. To effectively troubleshoot, start by examining the 'show version' section to confirm the hardware model, NX-OS version, and uptime. A recent reload may indicate a crash or power failure. Next, review 'show logging' for error messages, such as interface flaps, protocol adjacency changes, or hardware errors. Look for patterns: repeated errors at specific timestamps can pinpoint the onset of a problem.

The 'show interface brief' section provides a quick overview of interface status. Interfaces in 'down' state with reason 'notconnect' or 'err-disabled' indicate physical or configuration issues. Compare with 'show interface' for detailed counters; incrementing errors (CRC, runts, giants) suggest cabling or hardware faults. Routing issues are diagnosed via 'show ip route' and 'show ip ospf neighbor' (if OSPF is used). Missing routes or neighbors in 'FULL' state indicate protocol problems. The 'show spanning-tree' section helps identify topology changes or blocked ports causing loops.

For performance issues, examine 'show processes cpu' and 'show processes memory' within the tech-support output. High CPU utilization (above 80%) may be due to a routing protocol process or a broadcast storm. Memory leaks can cause crashes. The 'show system resources' section provides overall resource usage. If the issue is intermittent, compare multiple tech-support snapshots taken at different times. Finally, the 'show tech-support detail' option includes additional debug data, but use it sparingly due to its size. Always save the output to a file for historical comparison and for sharing with TAC. Remember that show tech-support is a point-in-time snapshot; for real-time monitoring, use commands like 'show interface counters' or 'monitor session'.

CCNA Exam Tips

Know that show tech-support is a collection of multiple show commands; you may be asked what information it includes.

Remember the 'file' option to save output; this is useful for TAC cases and is a common exam scenario.

Understand that the command can be resource-intensive; avoid running it during peak traffic in production.

Common Mistakes

Running show tech-support without 'no-more' on a live console, causing the session to hang while scrolling through pages.

Forgetting to specify a file destination and then losing the output when the terminal buffer overflows.

Assuming show tech-support captures real-time data; it is a snapshot and may not reflect transient issues.

Platform Notes

On Cisco NX-OS (Nexus), show tech-support is more comprehensive than on Cisco IOS. It includes additional sections such as 'show vpc', 'show fabricpath', 'show nve', and 'show system internal' commands that are specific to data center features. The output format is similar to IOS but with NX-OS-specific headers. On IOS, the equivalent command is 'show tech-support' as well, but the content differs: IOS includes 'show running-config', 'show startup-config', 'show version', etc., but lacks NX-OS-specific features like VPC or OTV. On IOS-XR, the command is 'show tech-support' but with a different structure and more extensive routing protocol details.

Version differences within NX-OS: In older versions (pre-7.0), the command may not support the 'feature' or 'section' options. Always check the documentation for your specific NX-OS version. On Nexus 9000 with ACI mode, the command is different; use 'show tech-support' in the APIC GUI or CLI. For Nexus 3000/3100 platforms, the command is identical but may have fewer sections due to simpler feature sets. The 'file' option is available on all NX-OS platforms. When running on virtual Nexus (NX-OSv), the output is similar but hardware-related sections may be minimal. Always use the 'no-more' option when capturing to a file to avoid truncation.

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