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

PDF

Attach a source interface

Updated: February 5, 2026

Overview

Use this procedure to attach a source interface to a monitor session for an Access Control List (ACL). This task covers entering interface configuration mode, applying the IPv4 access group, attaching a source interface, and specifying the direction of traffic to be replicated for monitoring.

Use these steps to attach a source interface to a monitor session for an ACL.

Procedure

1.

Enter global configuration mode.

Example:

Router# configure
2.

Enter interface configuration mode for the specified source interface in interface type number . The interface number is entered in rack/slot/module/port notation. For more information about the syntax for the router, use the question mark (?) online help function.

Example:

Router(config)# interface HundredGigE 0/1/0/10/0/1/0
3.

Control access to an interface in ipv4 access-group acl-name {ingress | egress} .

Example:

Router(config-if)# ipv4 access-group acl1 ingress
4.

Attach a monitor session to the source interface and enter the monitor session configuration mode.

Example:

Router(config-if)# monitor-session mon1 ethernet direction rx-only port-level acl
Router(config-if-mon)#
Note

rx-only specifies that only ingress traffic is replicated.
5.

Specify that the traffic mirrored is according to the defined ACL.

Example:

Router(config-if-mon)# acl
Note

f an ACL is configured by name, it overrides any ACL that may be configured on the interface.
6.

Exit the monitor session configuration mode and return to interface configuration mode.

Example:

Router(config-if-mon)# exit
Router(config-if)#
7.

Save configuration changes.

Example:

RP/0/RP0/CPU0(config-if)# end
or
RP/0/RP0/CPU0(config-if)# commit
When you execute the end command, the system prompts you to commit changes. 
Uncommitted changes found, commit them before exiting (yes/no/cancel)?
[cancel]:
  • yes - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.
  • no - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.
  • cancel - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
  • commit - Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
8.

Display information about the monitor session.

Example:

Router# show monitor-session status