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Objective 1.1.c Troubleshoot Err-disable Recovery

August 20, 2014 by Rowell Dionicio Leave a Comment

Err-disable RecoveryThe content on this page are my notes on objective 1.1.c – Troubleshoot Err-disable Recovery – of the CCNP SWITCH 300-115 Cisco certification. You can view the previous notes for objective 1.1.a – SDM Templates – and 1.1.b – Managing MAC Address Table.

Error Disable Recovery is the act of a switch detecting an error condition and then automatically turns the err-disabled interface back on after a default time. You can specify reasons for an interface to become re-enabled.

When a port goes into err-disabled it will shut down and stop sending and receiving traffic. The LED changes to orange and err-disabled will be shown under the show interfaces command.

The reason why an interface would go into err-disable is because of an error condition. This tells a network engineer there is a problem with the port and prevents the port from causing other ports to fail. Some of the causes for err-disable:

  • Bad cable
  • Bad network interface card
  • Port duplex mismatch
  • Port channel misconfiguration
  • BPDU guard violation
  • UDLD condition
  • Late-collision detection
  • Link-flap detection
  • Security violation
  • PAgP flap
  • L2TP guard
  • DHCP snooping rate-limit
  • Incorrect GBIC/SFP module or cable
  • ARP Inspection
  • Inline power

How do you determine the reason of err-disable

Type the command show errdisable recovery to display the ErrDisable Reason column and find out if you have autorecovery enabled. As you can see in the list below, autorecovery for all the features listed are disabled.

SW#show errdisable recovery
ErrDisable Reason Timer Status
----------------- --------------
udld Disabled
bpduguard Disabled
security-violatio Disabled
channel-misconfig Disabled
vmps Disabled
pagp-flap Disabled
dtp-flap Disabled
link-flap Disabled
l2ptguard Disabled
psecure-violation Disabled
sfp-config-mismat Disabled
gbic-invalid Disabled
dhcp-rate-limit Disabled
unicast-flood Disabled
storm-control Disabled
arp-inspection Disabled
loopback Disabled
Timer interval: 300 seconds
Interfaces that will be enabled at the next timeout:
SW#

To enable autorecovery use the following syntax:

errdisable recovery cause cause-name

Commands to use:

show interfaces interface_number status to check the Status column of the switchport.

SW#show interfaces g1/0/13 status
Port Name Status Vlan Duplex Speed Type
 Gi1/0/13 UPLINK notconnect 1 auto auto 10/100/1000BaseTX

show errdisable detect to show the current settings of errdisable. Mainly to check if errdisable detection is enabled for different settings.

SW#show errdisable detect
 ErrDisable Reason Detection status
 ----------------- ----------------
 udld Enabled
 bpduguard Enabled
 security-violatio Enabled
 channel-misconfig Enabled
 psecure-violation Enabled
 vmps Enabled
 loopback Enabled
 unicast-flood Enabled
 pagp-flap Enabled
 dtp-flap Enabled
 link-flap Enabled
 l2ptguard Enabled
 sfp-config-mismat Enabled
 gbic-invalid Enabled
 dhcp-rate-limit Enabled
 storm-control Enabled
 ilpower Enabled
 arp-inspection Enabled
 community-limit Enabled
 invalid-policy Enabled

show interfaces status err-disabled will display any interfaces currently in err-disabled status.

The show interfaces command will display whether the port is in error disabled mode.

To reenable an err-disabled port, you must shutdown the port and issue a no shutdown command. To automatically recover you must issue the errdisable recovery interval timer_interval_seconds command.

 

Related

Filed Under: Certification Tagged With: 300-115, ccnp, SWITCH

About Rowell Dionicio

I am Rowell Dionicio, a network engineer with a coffee addiction and a passion for Wi-Fi. Follow me on Twitter, LinkedIn, Facebook and YouTube.

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