What is Err-disable?
If the configuration shows a port to be enabled, but software on the switch detects an error situation on the port, the software shuts down that port. In other words, the port is automatically disabled by the switch operating system software because of an error condition that is encountered on the port.
When a port is error disabled, it is effectively shut down and no traffic is sent or received on that port. The port LED is set to the color orange.
If the configuration shows a port to be enabled, but software on the switch detects an error situation on the port, the software shuts down that port. In other words, the port is automatically disabled by the switch operating system software because of an error condition that is encountered on the port.
When a port is error disabled, it is effectively shut down and no traffic is sent or received on that port. The Causes of Errdisable
This feature was first implemented in order to handle special collision situations in which the switch detected excessive or late collisions on a port. Excessive collisions occur when a frame is dropped because the switch encounters 16 collisions in a row. Late collisions occur after every device on the wire should have recognized that the wire was in use.
Possible causes of these types of errors include:
A cable that is out of specification (either too long, the wrong type, or defective)
A bad network interface card (NIC) card (with physical problems or driver problems)
A port duplex misconfiguration
A port duplex misconfiguration is a common cause of the errors because of failures to negotiate the speed and duplex properly between two directly connected devices (for example, a NIC that connects to a switch). Only half-duplex connections should ever have collisions in a LAN. Because of the carrier sense multiple access (CSMA) nature of Ethernet, collisions are normal for half duplex, as long as the collisions do not exceed a small percentage of traffic.
There are various reasons for the interface to go into errdisable. The reason can be:
To chack if interface is in Err-disabled mode:
2960G# show interface gigabit0/7 GigabitEthernet0/7 is down, line protocol is down (err-disabled)
We can configure the switch to automatically re-enable any error-disabled interfaces after a specified timeout period.
Switch(config)# errdisable recovery cause psecure-violation Switch(config)# errdisable recovery interval 300
The above configuration enables auto-recovery for port security violations after five minutes. As evident in the list, autorecovery can apply to far more than just port security violations.
Commands useful in troubleshooting:
Switch# show errdisable recovery ErrDisable Reason Timer Status ----------------- -------------- arp-inspection Disabled bpduguard Disabled channel-misconfig Disabled dhcp-rate-limit Disabled dtp-flap Disabled gbic-invalid Disabled inline-power Disabled l2ptguard Disabled link-flap Disabled mac-limit Disabled link-monitor-failure Disabled loopback Disabled oam-remote-failure Disabled pagp-flap Disabled port-mode-failure Disabled psecure-violation Enabled security-violation Disabled sfp-config-mismatch Disabled storm-control Disabled udld Disabled unicast-flood Disabled vmps Disabled Timer interval: 300 seconds Interfaces that will be enabled at the next timeout:
Switch# show inerfaces status err-disabled ! Switch# errdisable recovery cause ! Switch# show log
More information:
http://packetlife.net/blog/2009/sep/14/errdisable-autorecovery/
Follow me!
