How do you fix an Errdisable port?
To recover a port that is in an Errdisable state, manual intervention is required, and the administrator must access the switch and configure the specific port with ‘shutdown’ followed by the ‘no shutdown’ command.
What is Errdisable state?
Errdisable is a feature that automatically disables a port on a Cisco Catalyst switch. When a port is error disabled, it is effectively shut down and no traffic is sent or received on that port. The error disabled feature is supported on most Catalyst switches running the Cisco IOS software.
What is BPDU Guard Cisco?
BPDU guard is a portfast feature that protects your spanning tree on edge ports (Access ports). It (in layman’s terms) monitors your port for BPDUs. If it see’s one (presumably from an unauthorized switch, hub or host), it shuts the port down (err-disabled).
What is the purpose of BPDU guard?
BPDU Guard feature is used to protect the Layer 2 Spanning Tree Protocol (STP) Topology from BPDU related attacks. BPDU Guard feature must be enabled on a port that should never receive a BPDU from its connected device.
What causes Errdisable?
The errdisable reason can be: Duplex mismatch. Port channel misconfiguration. BPDU guard violation.
What are two reasons why a switch port would have a status of Errdisable?
The reasons a catalyst switch can go into Errdisable mode and shutdown a port are many and include:
- Duplex Mismatch.
- Loopback Error.
- Link Flapping (up/down)
- Port Security Violation.
- Unicast Flodding.
- UDLD Failure.
- Broadcast Storms.
- BPDU Guard.
How does BPDU filter work?
As the name says, BPDU filter filters BPDUs in both directions. BPDU filter will prevent inbound and outbound BPDU but will remove portfast state on a port if a BPDU is received. Enabling BPDU filtering on an interface is the same as disabling spanning tree on it and can cause spanning-tree loops.
What does port fast do?
Enabling the PortFast feature causes a switch or a trunk port to enter the STP forwarding-state immediately or upon a linkup event, thus bypassing the listening and learning states. The PortFast feature is enabled at a port level, and this port can either be a physical or a logical port.
What are two reasons why a switch port would have a status of Errdisable choose two?
There are various reasons for the interface to go into errdisable….The errdisable reason can be:
- 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.
What can be done to bring a switch port to the operational state from the Errdisable state?
What can be done to bring a switch port to the operational state from the ERRDISABLE state? The administrator needs to issue the command shutdown and then no shutdown to reenable the port.
