ICNDI-2 Spanning Tree Protocol

Question 1

What is the Bridge ID?

Answer 1

This is a unique identification number of each switch in the network. It consists of bridge priority and the base MAC Address of the switch

Question 2

What is the default bridge priority of a cisco switch?

Answer 2

32768. This is a configurable value between 0 to 61440 but the value has to be in increments of 4096. 4096, 8192, 12288, so on and so forth are acceptable values

Question 3

What is the Root Bridge?

Answer 3

All switches in the network elect the root of the tree. The switch with the lowest Bridge ID wins the election.

Question 4

What is the role of the Root Bridge?

Answer 4

All decisions such as which redundant path to block and which to open are taken from the perspective of the root switch

Question 5

What is a designated port?

Answer 5

The port with the lowest cost on a switch with redundant ports, connecting it to a LAN segment

Question 6

What are the five states of switch ports running STP?

Answer 6

Blocked, Listening, Learning, Forwarding, Disabled

Question 7

What is the Switch port Blocked state?

Answer 7

None of the ports will transmit or receive any data, but they will listen to BPDUs. The BPDU carries various pieces of information that are used by STP to determine what state the ports should be in and what the STP topology should be.

Question 8

What is the Switch Port Listening State?

Answer 8

The switch listens for frames but doesn’t learn or act on them. The switch does receive the frames but discards them before any action is taken. MAC addresses are not placed into the CAM table while the port is listening.

Question 9

What is the Switch Port Learning State?

Answer 9

The switch will start to learn MAC addresses it can see and will populate its CAM table with the addresses and the ports on which they were found. In this state, the switch will start to transmit its own BPDUs

Question 10

What is the Switch Port Forwarding State?

Answer 10

The switch has learned MAC addresses and corresponding ports and populates its CAM table with this. The switch can now forward traffic

Question 11

What is the Switch port Disable State?

Answer 11

In the Disabled state, the port will receive BPDUs but will not forward them to the switch processor. It discards all incoming frames from both the port and other forwarding ports on the switch.

Question 12

After What 3 steps is STP converged?

Answer 12

Elect root bridge
Elect root ports
Elect designated ports