Traffic Mirroring Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Release

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Troubleshoot traffic mirroring issues

Updated: March 2, 2026

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Overview

Learn how to identify and resolve traffic mirroring issues by using monitor session status commands. This procedure explains how to interpret session and source interface status messages to correct configuration errors, inactive interfaces, or operational failures.

When you encounter any issue with traffic mirroring, begin troubleshooting by checking the output of the show monitor-session status command.

Procedure

1.

Use the show monitor-session status command when you encounter any issue with traffic mirroring. This command displays the recorded state of all sessions and source interfaces:

Example:


Monitor-session sess1
<Session status>
================================================================================
Source Interface   Dir  Status
--------------------- ---- ----------------------------------------------------
Gi0/0/0/0       Both <Source interface status>
Gi0/0/0/2       Both <Source interface status>

The <Session status> indicates one of these configuration errors:

Session Status

Explanation

Session is not configured globally

The session does not exist in global configuration. Check show run command output to ensure that a session with a correct name has been configured.

Destination interface <intf> is not configured

The interface that has been configured as the destination does not exist. For example, the destination interface may be configured as a VLAN subinterface, but the VLAN subinterface may not yet be created.

Destination interface <intf> (<down-state>)

The destination interface is not in Up state in the Interface Manager. You can verify the state using the show interfaces command.

Check the configuration to see what might be keeping the interface from coming up. For example, a sub-interface needs to have an appropriate encapsulation configured.

<Source interface status> reports these messages:

Source Interface Status

Explanation

Operational

Everything appears to be working correctly in traffic mirroring PI. Please follow up with the platform teams in the first instance if mirroring is not operating as expected.

Not operational (Session is not configured globally)

The session does not exist in global configuration. Check the show run command output to ensure that a session with the right name has been configured.

Not operational (destination interface not known)

The session exists, but it either does not have a destination interface specified, or the destination interface named for the session does not exist (for example, if the destination is a sub-interface that has not been created).

Not operational (source same as destination)

The session exists, but the destination and source are the same interface, so traffic mirroring does not work.

Not operational (destination not active)

The destination interface or pseudowire is not in the Up state. See the corresponding Session status error messages for suggested resolution.

Not operational (source state <down-state>)

The source interface is not in the Up state. You can verify the state using the show interfaces command. Check the configuration to see what might be keeping the interface from coming up (for example, a sub-interface needs to have an appropriate encapsulation configured).

Error: see detailed output for explanation

Traffic mirroring has encountered an error. Run the show monitor-session status detail command to display more information.

2.

Use the show monitor-session status detail command to display full details of the configuration parameters, and of any errors encountered.

Example:

Router#show monitor-session status detail
Monitor-session sess1
 Destination interface is not configured
 Source Interfaces
 -----------------
 HundredGigE0/0/0/0
  Direction: Both
  ACL match: Enabled
  Portion:  Full packet
  Status:  Not operational (destination interface not known)
 HundredGigE0/0/0/2
  Direction: Both
  ACL match: Disabled
  Portion:  First 100 bytes
  Status: Not operational (destination interface not known). Error: 'Viking SPAN PD' detected the 'warning' condition 'PRM connection creation failure'.
Monitor-session foo
 Destination next-hop HundredGigE 0/0/0/0
 Source Interfaces
 -----------------
 HundredGigE 0/1/0/0.100:
  Direction: Both
  Status:  Operating
 HundredGigE 0/2/0/0.200:
  Direction: Tx
  Status:  Error: <blah>

Monitor session bar
 No destination configured
 Source Interfaces
 -----------------
 HundredGigE 0/3/0/0.100:
  Direction: Rx
  Status:  Not operational(no destination)

What to do next

After configuring an Ethernet interface, you can configure individual VLAN subinterfaces on the Ethernet interface.

For information about modifying Ethernet management interfaces for the shelf controller (SC), route processor (RP), and distributed RP, see the Advanced Configuration and Modification of the Management Ethernet Interface later in this document.

For information about IPv6, see the Implementing Access Lists and Prefix Lists on Cisco IOS XR Software module in the Cisco IOS XR IP Addresses and Services Configuration Guide.