2.1.a (ii) Errdisable Recovery

This section will be used to build notes and flash cards for 2.1.a (ii) Errdisable Recovery.

Err-disabled is a port state which prohibits sending and reciving traffic, it effectively means the port is down for some error related reason.

How do you know it’s err-disabled?

1.To view a ports status you can use:
Look for the status column and for the value of “err-disabled”.
show int status
show int g0/1 status

2.You may have also gotten a syslog message if you have logging setup to a server.
Alternatively you can just view the old logs in buffer by running
show logging

3. Use “show errdisable recovery” if you have “errdisable recovery cause” to show you the reason it was turned off

How do you manually recover an errdisabled port?
shut
no shut

By default all of these below causes are enabled for err-disabled and will cause a port to go down:

Duplex mismatch
Port channel misconfiguration
BPDU guard violation
UniDirectional Link Detection (UDLD) condition
Late-collision detection
Link-flap detection
Security violation
Port Aggregation Protocol (PAgP) flap
Layer 2 Tunneling Protocol (L2TP) guard
DHCP snooping rate-limit
Incorrect SFP
Address Resolution Protocol (ARP) inspection
Inline power issue

To turn one of these off use:
conf t
no errdisable detect cause

The show command verification for checking which are on or off is:
show errdisable detect

You should be aware errdisable recovery is turned off by default.

To turn it on for all reasons use:
errdisable recovery cause all

The default timeout for errdisable recovery is 300 seconds before it tries to recover again.

To change the errdisable recovery interval use the following commands:
conf t
errdisable recovery interval

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/69980-errdisable-recovery.pdf