STP Interview Questions 2

Question 1

How is the Root Bridge elected?

Answer 1

• The switch with the lowest Bridge ID is elected as the Root bridge.
• The Bridge ID is 8 bytes long and includes the priority (32678) and the MAC address of the device and the VLAN ID.

Question 2

Explain Root path cost.

Answer 2

Root path cost is the combination cost of all links to the Root Bridge.

Question 3

How Root Ports are elected?

Answer 3

The port with the lowest root path cost is elected as the root port and is placed in the forwarding state.

Question 4

What is the difference between Path cost and Root Path cost?

Answer 4

• Path cost is the value assigned to each port.
• Root path cost is defined as the combined cost to reach the root bridge.

Question 5

What is Root Port?

Answer 5

Once the root switch is elected, every other Switch in the network must select a single port on itself to reach the Root Switch.

The single selected port on a Switch with the least Path Cost to reach the Root Bridge is called the Root Port.