– bpduguard: Detects when a spanning-tree bridge protocol data unit (BPDU) is received on a port configured for STP PortFast – arp-inspection: Detects errors with dynamic ARP inspection One of the following triggers the errdisable state: You can repeat this command to enable or disable more than one cause.
Use the following command in global configuration mode, here is the command syntax: Switch(config)# errdisable detect cause You can tune this behavior so that only certain causes trigger any port being disabled. If an error condition is detected, the switch port is put into the “errdisable” state and is disabled. If a serious error occurs on a switch port, that port can be shut down automatically until someone manually enables the port again, or until a predetermined time has elapsed.īy default, a switch detects an error condition on every switch port for every possible cause. If so, an alert can be issued so that someone can take action to correct the problem. Switches can detect error conditions automatically, without any further help. A switch can be polled periodically with SNMP so that its port error counters can be examined to see whether an error condition has occurred. Managing Error Conditions on a Switch PortĪ network-management application can be used to detect a serious error condition on a switch port. The show errdisable detect command displays the error-disable detection status. In order to disable error-disable detection, use the no errdisable detect cause command. Note: Error-disable detection is enabled for all of these reasons by default.
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A bad network interface card with physical problems or driver problemsĪ 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.A cable that is out of specification (either too long, the wrong type, or defective).Possible causes of these types of errors include: Late collisions occur after every device on the wire should have recognized that the wire was in use. Excessive collisions occur when a frame is dropped because the switch encounters 16 collisions in a row. This feature was first implemented to handle special collision situations in which the switch detected excessive or late collisions on a port. The error disable feature helps prevent these situations. Such a failure can occur when a bad port monopolizes buffers or port error messages monopolize interprocess communications on the card, which can ultimately cause serious network issues. The actual message depends on the reason for the error condition. The error disable function serves two purposes:ġ- It lets the administrator know when and where there is a port problem.Ģ- It eliminates the possibility that this port can cause other ports on the module (or the entire module) to fail. This message is displayed when a host port receives the BPDU. Disabling port.īpduguard error detected on Gi4/1, putting Gi4/1 in err-disable state Received BPDU on port GigabitEthernet4/1 with BPDU Guard enabled. If the interface has been disabled because of an error condition, you can see log messages that are similar to these in both the console and the syslog: %SPANTREE-SP-2-BLOCK_BPDUGUARD: Here is an example of what an error-disabled port looks like from the command-line: Switch# show interfaces gigabitethernet 4/1 status The port LED is set to the color orange and, when you issue the show interfaces command, the port status shows err-disabled. When a port is error disabled, it is effectively shut down and no traffic is sent or received on that port.
The port is automatically disabled by the switch IOS because of an error condition that is encountered on the port.
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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. The way in which errdisable is implemented varies between software platforms, I’ll be covering on errdisable for switches that run Cisco IOS Software only.
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