17 - Spanning Tree Part 1

Question 1

‘Classic’ Spanning Tree Protocol is IEEE […]

Answer 1

802.1D

Question 2

Cisco switches use a version of STP called […], which runs a separate spanning tree instance in each VLAN.

Answer 2

PVST (Per-Vlan Spanning Tree)

Question 3

Do all switches run STP by default?

Answer 3

Yes

Question 4

How many root bridges are elected in STP?

Answer 4

One

Question 5

If looped Layer 2 broadcast messages accumulate and congest a network, this is called a […]

Answer 5

broadcast storm

Question 6

In an 802.1D STP network, which switch(es) send BPDUs?

Answer 6

Root bridge only

Question 7

Interface Speed: 1 Gbps
802.1D STP cost: […]

Answer 7

4

Question 8

Interface Speed: 10 Gbps
802.1D STP cost: […]

Answer 8

2

Question 9

Interface Speed: 10 Mbps
802.1D STP cost: […]

Answer 9

100

Question 10

Interface Speed: 100 Mbps
802.1D STP cost: […]

Answer 10

19

Question 11

Interface Speed: […]
802.1D STP cost: 100

Answer 11

10 Mbps

Question 12

Interface Speed: […]
802.1D STP cost: 19

Answer 12

100 Mbps

Question 13

Interface Speed: […]
802.1D STP cost: 2

Answer 13

10 Gbps

Question 14

Interface Speed: […]
802.1D STP cost: 4

Answer 14

1 Gbps

Question 15

STP Designated ports are in a […] state.

Answer 15

forwarding

Question 16

STP Non-Designated ports are in a […] state

Answer 16

blocking

Question 17

STP root port selection:
1: Lowest […]
2: Lowest […]
3: Lowest […]

Answer 17

1. root cost
2. neighbor bridge ID
3. neighbor port ID

Question 18

STP Root ports are in a […] state.

Answer 18

forwarding

Question 19

STP: All ports on the root bridge are […] ports (forwarding state)

Answer 19

designated

Question 20

STP: The default bridge priority is […] (not including Extended System ID)

Answer 20

32768

Question 21

STP: The switch with the lowest […] becomes the root bridge.

Answer 21

Bridge ID

Question 22

STP: There must be one […] port per collision domain.

Answer 22

designated

Question 23

STP: There must be one designated port per […].

Answer 23

collision domain

Question 24

STP: When a switch is powered on, it assumes the role of […] bridge.

Answer 24

root

Question 25

The messages sent by STP switches are called:

Answer 25

BPDUs (Bridge Protocol Data Units)

Question 26

The STP bridge priority can be changed in units of […]

Answer 26

4096

Possible values (you don’t have to memorize these!):
0, 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768, 36864, 40960, 45056, 49152, 53248, 57344, or 61440

Question 27

Three fields of the STP Bridge ID:
[…] (4 bits)
Extended System ID (12 bits)
MAC Address (48 bits)

Answer 27

Bridge Priority

Question 28

Three fields of the STP Bridge ID:
Bridge Priority (4 bits)
[…] (12 bits)
MAC Address (48 bits)

Answer 28

Extended System ID (VLAN ID)

Question 29

Three fields of the STP Bridge ID:
Bridge Priority (4 bits)
Extended System ID (12 bits)
[…] (48 bits)

Answer 29

MAC Address

Question 30

Three fields of the STP Bridge ID:
Bridge Priority (4 bits)
Extended System ID (12 bits)
MAC Address ([…] bits)

Answer 30

48

Question 31

Three fields of the STP Bridge ID:
Bridge Priority (4 bits)
Extended System ID ([…] bits)
MAC Address (48 bits)

Answer 31

12

Question 32

Three fields of the STP Bridge ID:
Bridge Priority ([…] bits)
Extended System ID (12 bits)
MAC Address (48 bits)

Answer 32

4

Question 33

What does BPDU stand for?

Answer 33

Bridge Protocol Data Unit

Question 34

What does PVST stand for?

Answer 34

Per-VLAN Spanning Tree

Question 35

When a switch rapidly and continuously updates a MAC address in its MAC address table, alternating between different interfaces, this is known as […]

Answer 35

MAC address flapping

Question 36

Which field in the STP BPDU is used to elect the root bridge?

Answer 36

Bridge ID field