Cisco INFRA-ESD-6-PORT_STATE_CHANGE_LINK_DOWN Triage

Seeing INFRA-ESD-6-PORT_STATE_CHANGE_LINK_DOWN in the syslog of a Cisco IOS XR router can be alarming, but it is usually a routine module reload artifact — or, when it persists, a solvable control-plane link issue. This article explains what the message actually means, how to map the failing CE switch port to its peer, and the exact reset/reload sequence for Cisco 8000, ASR 9000 and NCS 5500 platforms, based on the official Cisco TAC document.

What the Error Message Means

The Ethernet Switch Driver (ESD) provides VLAN-based L2 switching for the Control Ethernet (CE) switches — also called EOBC switches — that connect the RP, line cards and System Controller inside the chassis. The message simply reports that a CE switch port's physical link went down. It is completely normal during module reload or boot failure; the port must come back up once the module finishes booting. The problem is when the message persists or flaps while the module is up.

Triage: Find the Port and Its Peer

On ASR 9000 eXR, start in admin mode and map the port:

admin# show controller switch reachable
admin# show controller switch summary location 0/LC2/LC-SW
admin# show controller switch statistics location 0/LC2/LC-SW

The summary shows port number, physical/admin state and what the port connects to. If physical is down while admin is up, the far end is not bringing the link up — check the peer location with the same commands.

Recovery: Reset Port, Reload Module, Reseat

admin# controller switch port-state location 0/LC2/LC-SW 33 down
admin# controller switch port-state location 0/LC2/LC-SW 33 up
admin# reload location 0/2 all

Work through the escalation ladder: reset the specific port, then fully reload the module (reload location 0/2 all on eXR; hw-module location 0/1/CPU0 reload on cXR), then physically reseat or OIR the module. On NCS 5500 all CE switch commands run in admin mode, and reload location force from EXEC mode does not reset the onboard CE switch — use hw-module loc 0/2 reload.

Escalation Data Collection

show tech-support
show tech-support ethernet controllers
admin show tech-support control-ethernet

If the port still flaps after reset and reseat, collect these files and open a TAC case. For related platform-level checks see the IOS XR TAC command list and Nexus vPC failover troubleshooting.

原文链接：https://www.cisco.com/c/en/us/support/docs/routers/8808-router/221204-troubleshoot-the-error-message-infra-esd.html