BPDU Guard

Q: How deeply does Acing the CCNA Exam: Volume 1 Fundamentals and Protocols cover BPDU Guard?

Explains triggering, error-disabled consequences, verification, and manual recovery, but does not detail automatic recovery.

As explained in Acing the CCNA Exam: Volume 1 Fundamentals and Protocols

BPDU Guard is a switch-port protection feature that places a port into an error-disabled state when the port receives a Bridge Protocol Data Unit.

BPDU Guard protects end-host switch ports from unexpected Spanning Tree Protocol (STP) messages. When a protected port receives a Bridge Protocol Data Unit (BPDU), the switch places the port into an error-disabled state. section 14.5 section 14.5.2

Use BPDU Guard with PortFast on ports intended only for end hosts:

Configure a specific interface with spanning-tree bpduguard enable. section 14.5.2
Use spanning-tree portfast bpduguard default globally to enable it on all PortFast-enabled ports. section 14.5.2
If someone connects another switch, the received BPDU triggers protection before that switch can affect the STP topology, such as becoming the root bridge. section 14.5.2

Unexpected switch connection

A PortFast-enabled access port is accidentally connected to another switch. BPDU Guard detects the other switch's BPDU and disables the port. The port becomes nonoperational and appears as down/down in show ip interface brief. After disconnecting the offending switch, reset the port with shutdown followed by no shutdown. section 14.5.2

How Acing the CCNA Exam: Volume 1 Fundamentals and Protocols covers it

Cover of Acing the CCNA Exam: Volume 1 Fundamentals and Protocols

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Related concepts

error-disabled stateproduces · An error-disabled state is a switch-port state in which the device disables the port after detecting a configured error or protection violation.
bridge protocol data unituses · A bridge protocol data unit is a control message exchanged by spanning-tree-enabled switches to communicate topology information and determine port roles.
spanning tree protocolkind of · Spanning Tree Protocol is a Layer 2 protocol that prevents bridged-network loops by selecting a loop-free topology and blocking redundant paths.
PortFastuses · PortFast is a Cisco spanning-tree feature that allows an access port connected to an end host to enter the forwarding state without the usual transition delay.
IEEE 802.1wuses · IEEE 802.1w is the IEEE standard that specifies Rapid Spanning Tree Protocol.

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 1 Fundamentals and Protocols. The section links point to the parts of the book it draws on.