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

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Configure layer 3 ACL-based traffic mirroring

Updated: March 2, 2026

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Overview

Use this procedure to configure traffic mirroring for Layer 3 Access Control Lists (ACLs). This task includes starting a monitor session, defining a tunnel destination, and applying the capture keyword within the ACL to initiate the mirroring of specific IPv4 traffic.

Use these steps to configure traffic mirroring for layer 3 ACLs.

Procedure

1.

Start a monitor session.

Example:

Router# configure
Router(config)# monitor-session ms1
2.

Define a destination.

Example:

Router(config-mon)# destination tunnel-ip 1
Router(config-mon)# commit
3.

Attach an interface to the monitor session for an acl and specify the direction for which you want to mirror the traffic.

Example:

Router# configure
Router(config)# interface HundredGigE/2/0/11
Router(config-if)# ipv4 access-group span ingress
Router(config-if)# monitor-session ms1 ethernet direction rx-only acl
Router(config-if-mon)# commit
4.

Use the capture keyword to start mirroring traffic for the ACL.

Example:

Router# configure
Router(config)# ipv4 access-list span
Router(config-ipv4-acl)# 5 permit ipv4 any any dscp 5 capture
Router(config-ipv4-acl)# 10 permit ipv4 any any
Router(config-ipv4-acl)# commit