Error-Disabled State; Mtu Configuration - Cisco Nexus 3548 Configuration Manual

Configuring Layer 2 Interfaces

Error-Disabled State

An interface is in the error-disabled (err-disabled) state when the inteface is enabled administratively (using
the no shutdown command) but disabled at runtime by any process. For example, if UDLD detects a
unidirectional link, the interface is shut down at runtime. However, because the interface is administratively
enabled, the interface status displays as err-disabled. Once an interface goes into the err-disabled state, you
must manually reenable it or you can configure an automatic timeout recovery value. The err-disabled detection
is enabled by default for all causes. The automatic recovery is not configured by default.
When an interface is in the err-disabled state, use the errdisable detect cause command to find information
about the error.
You can configure the automatic err-disabled recovery timeout for a particular err-disabled cause by changing
the time variable.
The errdisable recovery cause command provides automatic recovery after 300 seconds. To change the
recovery period, use the errdisable recovery interval command to specify the timeout period. You can specify
30 to 65535 seconds.
To disable recovery of an interface from the err-disabled state, use the no errdisable recovery cause command.
The various options for the errdisable recover cause command are as follows:
• all—Enables a timer to recover from all causes.
• bpduguard—Enables a timer to recover from the bridge protocol data unit (BPDU) Guard error-disabled
• failed-port-state—Enables a timer to recover from a Spanning Tree Protocol (STP) set port state failure.
• link-flap—Enables a timer to recover from linkstate flapping.
• pause-rate-limit—Enables a timer to recover from the pause rate limit error-disabled state.
• udld—Enables a timer to recover from the Unidirectional Link Detection (UDLD) error-disabled state.
• loopback—Enables a timer to recover from the loopback error-disabled state.
If you do not enable the err-disabled recovery for the cause, the interface stays in the err-disabled state until
you enter the shutdown and no shutdown commands. If the recovery is enabled for a cause, the interface is
brought out of the err-disabled state and allowed to retry operation once all the causes have timed out. Use
the show interface status err-disabled command to display the reason behind the error.

MTU Configuration

The Cisco Nexus device switch does not fragment frames. As a result, the switch cannot have two ports in
the same Layer 2 domain with different maximum transmission units (MTUs). A per-physical Ethernet interface
MTU is not supported. Instead, the MTU is set according to the QoS classes. You modify the MTU by setting
class and policy maps.
Note
When you show the interface settings, a default MTU of 1500 is displayed for physical Ethernet interfaces.
state.
Cisco Nexus 3548 Switch NX-OS Interfaces Configuration Guide, Release 9x
Error-Disabled State
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