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

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Guidelines for mirroring forward-drop packets

Updated: March 2, 2026

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Overview

This section provides the guidelines for configuring forward-drop packet mirroring on a router. It includes information on global session limits, traffic-class behavior, and handling in-band traffic destined for the management interface.

These guidelines apply to mirroring forward-drop packets:

  • Only one global forward-drop session can be configured on a router.

  • When traffic-class is configured under monitor-session for forward-drop, the Type of Service (ToS) byte of the outgoing ERSPAN packet is overwritten with the configured traffic-class value.

  • In-band traffic destined to router management interface cannot be captured using this functionality.

  • For ERSPAN sessions that monitor forward-drop packets, a default value of 0 is used for the encapsulation traffic class, irrespective of the DSCP value assigned for the tunnel.