Root Guard Functionality

Which of the following BEST describes the functionality of the root guard feature on a switch?

A.

BPDUs entering the root bridge are ignored.

B.

The STP root bridge cannot be changed.

C.

Broadcast storms entering from a root port are blocked.

D.

Loop protection is enabled on the root port of a switch.

B.

Sure, I'd be happy to explain each of the options and which one BEST describes the functionality of the root guard feature on a switch.

A) BPDUs entering the root bridge are ignored: This option does not accurately describe the functionality of the root guard feature. While the root guard feature does prevent unauthorized switches from becoming the root bridge, it does not ignore BPDUs entering the root bridge.

B) The STP root bridge cannot be changed: This option also does not accurately describe the functionality of the root guard feature. The root guard feature does not prevent the STP root bridge from being changed, but rather prevents unauthorized switches from becoming the root bridge.

C) Broadcast storms entering from a root port are blocked: This option describes a different feature of switches called storm control. Storm control can be used to monitor and control the rate of broadcast, multicast, or unicast traffic that enters a switch port to prevent broadcast storms. This option is not describing the functionality of the root guard feature.

D) Loop protection is enabled on the root port of a switch: This option also does not accurately describe the functionality of the root guard feature. Loop protection is a different feature that is used to prevent loops from forming in a network by blocking ports that could potentially create a loop. The root guard feature is used to protect the root bridge from unauthorized switches.

So, the correct answer is B) The STP root bridge cannot be changed. The root guard feature is used to prevent unauthorized switches from becoming the root bridge in a Spanning Tree Protocol (STP) network. It does this by blocking superior BPDUs from switches that are not designated as the root bridge. This helps ensure that the network topology remains stable and prevents any accidental changes to the root bridge.