ACSP Spanning Tree Protocol (STP) 4

Question 1

Which RSTP proposal-agreement mechanism element must be true for a port to rapidly transition to Forwarding without going through full STP timers?

Accepted Answer

The link must be point-to-point full-duplex

Answer

RSTP rapid transition via proposal-agreement requires a point-to-point link, which is automatically detected on full-duplex connections.

Question 2

In MSTP, what is the maximum number of MST instances that can be configured (excluding MSTI 0/CIST)?

Accepted Answer

15

Answer

IEEE 802.1Q allows up to 64 MST instances total (0-63), with MSTI 0 reserved as the CIST, leaving 63 configurable instances, but most vendors limit this to 15 or 16.

Question 3

What STP feature disables a PortFast-enabled port when it receives a BPDU, protecting against accidental switch connections?

Accepted Answer

BPDU Guard

Answer

BPDU Guard err-disables a port upon receiving any BPDU, preventing switches from being connected to PortFast ports and disrupting the topology.

Question 4

Which spanning tree mode on Aruba switches is recommended for modern networks with multiple VLANs to provide per-VLAN load balancing?

Accepted Answer

MSTP (802.1s)

Answer

MSTP (802.1s) maps multiple VLANs to a smaller number of spanning tree instances, enabling per-group load balancing while reducing control plane overhead.

Question 5

A switch's root port has failed. In RSTP, which port transitions to Forwarding most quickly to restore connectivity?

Accepted Answer

The Alternate port

Answer

The RSTP Alternate port already holds a pre-computed alternate path to the root and can immediately transition to Forwarding when the root port fails, without waiting for timers.

(ACSP) Aruba Certified Switching Professional Practice Test

(ACSP) Aruba Certified Switching Professional Practice Test

ACSP Spanning Tree Protocol (STP) 4