STP Clinical & Scientific Knowledge 3

Question 1

What is the purpose of the PortFast feature in STP?

Accepted Answer

Allows edge ports to skip Listening and Learning states

Answer

PortFast allows access layer ports connected to end hosts to immediately transition to Forwarding, bypassing Listening and Learning.

Question 2

Which field in the Bridge ID has the highest priority during root bridge election?

Accepted Answer

Bridge priority

Answer

The bridge priority (default 32768) is compared first; the MAC address is only used as a tiebreaker.

Question 3

BPDUGuard is enabled on a PortFast port. What happens when a BPDU is received?

Accepted Answer

The port is placed in err-disabled state

Answer

BPDUGuard shuts down a PortFast port by placing it in err-disabled state if any BPDU is received.

Question 4

In RSTP (802.1w), which port role replaces the STP Blocking state ports?

Accepted Answer

Alternate and Backup ports

Answer

RSTP introduces Alternate (replaces blocked non-designated) and Backup (provides redundancy on shared segments) port roles.

Question 5

What STP path cost value is assigned to a 1 Gbps link using the original (short) path cost method?

Accepted Answer

4

Answer

Using the original 802.1D short path cost method, a 1 Gbps link has a cost of 4.

(STP) Spanning Tree Protocol Practice Test