STP

Question 1

What is the real-world analogy for Root Bridge?

Answer 1

City Hall / Central Hub

Question 2

What does Path Cost represent in a real-world analogy?

Answer 2

Road Speed Limit / Travel Time

Question 3

What is the analogy for Blocking Port?

Answer 3

Closed Road (for safety)

Question 4

What does Designated Port refer to in a real-world analogy?

Answer 4

Best Road to a neighborhood

Question 5

What is the real-world analogy for Redundant Link?

Answer 5

Extra Road — used only if needed

Question 6

What does Topology Change represent in a real-world analogy?

Answer 6

Traffic Reroute due to accident

Question 7

What is the main purpose of STP in a network?

Answer 7

To prevent layer 2 loops and broadcast storms by disabling redundant paths.

Question 8

What is the STP equivalent of the “central hub” in a city road system?

Answer 8

The Root Bridge.

Question 9

How does STP determine the “best” path to the Root Bridge?

Answer 9

By calculating the lowest path cost, based on link speed.

Question 10

What happens to ports that could cause loops but aren’t needed for the best path?

Answer 10

They are put into a Blocking state.

Question 11

A port on a non-root bridge that forwards traffic toward the root is called what?

Answer 11

A Root Port.

Question 12

On a segment, the switch with the best path to the root becomes what?

Answer 12

The Designated Bridge, and its port is the Designated Port.

Question 13

STP reconfigures the network when what happens?

Answer 13

A topology change (like a link or switch going down).

Question 14

What’s the default STP priority value for all switches?

Answer 14

32,768 — unless manually changed.

Question 15

If two switches have the same priority, how does STP break the tie?

Answer 15

By choosing the switch with the lowest MAC address.

Question 16

What STP port state allows a port to listen to BPDUs but not forward traffic yet?

Answer 16

Listening (and then Learning before Forwarding).

Question 17

What IEEE standard defines RSTP?

Answer 17

802.1w

Question 18

What’s the biggest improvement RSTP has over classic STP?

Answer 18

Faster convergence (1–2 seconds)

Question 19

Which RSTP port role replaces a blocked port with a backup path to the root bridge?

Answer 19

Alternate Port

Question 20

What are the three port states in RSTP?

Answer 20

Discarding, Learning, and Forwarding

Question 21

Is RSTP backward compatible with 802.1D STP?

Answer 21

Yes

Question 22

What does PVST stand for?

Answer 22

Per-VLAN Spanning Tree

Question 23

What vendor developed PVST and PVST+?

Answer 23

Cisco

Question 24

Why is PVST useful for VLANs?

Answer 24

It allows a separate spanning tree per VLAN, enabling load balancing.

Question 25

What’s the key difference between PVST and standard STP?

Answer 25

PVST runs one STP instance per VLAN; standard STP runs one for the entire network.

Question 26

What does the '+' in PVST+ mean?

Answer 26

It adds compatibility with standard (IEEE) STP switches.