Spanning Tree Protocol

Question 1

What command is used to prevent a new unconfigured switch from being elected root

Answer 1

spanning-tree guard root

Question 2

When STP is used, what is used to prevent newly introduced switches from being elected as the new root switch?

Answer 2

root guard

Question 3

When STP is used, which device will be elected root?

Answer 3

the device with the lowest switch priority

Question 4

What can you enable to ensure that a port immediately transitions to the STP forwarding state?

Answer 4

PortFast

Question 5

What two STP states are bypassed when using PortFast?

Answer 5

listening and learning

Question 6

What feature prevents nondesignated ports from inadvertently forming bridging loops if the steady flow of BPDUs is interrupted?

Answer 6

loop guard

Question 7

When a switchport stops receiving BPDUs, what state will loop guard put the port into?

Answer 7

loop inconsistent state which keep the port in a blocking state

Question 8

What command will enable loop guard for the entire switch?

Answer 8

spanning-tree loopguard default

Question 9

What command will enable loop guard for specific ports?

Answer 9

spanning-tree guard loop

Question 10

What is used to disable ports that erroneously receive BPDUs?

Answer 10

BPDU guard

Question 11

When BPDU guard is applied, the reciept of a BPDU on a port will result in the port being placed into what state?

Answer 11

error-disabled state

Question 12

What command can be used to automatically recover from a BPDU guard induced error-disable state?

Answer 12

errdisable recovery cause bpdugaurd and

errdisable recovery interval {interval value]

Question 13

In STP, what is the switch with the lowest bridge ID called?

Answer 13

root bridge

Question 14

What is the Bridge ID composed of?

Answer 14

Two byte bridge priority and a 6 byte MAC address

Question 15

If two or more switches have the lowest priority then what is used to determine the root bridge?

Answer 15

lowest MAC address

Question 16

What is the Port ID composed of?

Answer 16

port priority and port number

Question 17

What are ports on a root bridge always considered to be?

Answer 17

designated ports

Question 18

How many port states does Spanning Tree Protocol (STP) have?

Answer 18

5

Question 19

What are the STP port states?

Answer 19

disabled, blocking, listening, learning, forwarding

Question 20

How many port states does Rapid Spanning Tree Protocol have?

Answer 20

3

Question 21

What are the RSTP port states?

Answer 21

discarding, learning, forwarding

Question 22

What is VTP used for?

Answer 22

to synchronize VTP and Vlan configuration information between switches.

Question 23

What must match on all switches in for switches to synchronize information over VTP?

Answer 23

VTP domain name, VTP password, VTP version

Question 24

what is the command to manually set the bridge priority?

Answer 24

spanning-tree priority [value]

Question 25

What is the default bridge priority?

Answer 25

32768

Question 26

The time period between Hellos created by the STP root.

Answer 26

Hello timer

Question 27

How long any switch should wait, after ceasing to hear Hellos, before trying to change the STP topology.

Answer 27

MaxAge timer

Question 28

Delay that affects the process that occurs when an interface changes from blocking state to forwarding state. A port stays in an interim listening state, and then an interim learning state, for the number of seconds defined by the forward delay timer.

Answer 28

Forward delay timer

Question 29

Default Hello timer

Answer 29

2 seconds

Question 30

Default MaxAge

Answer 30

10 times Hello

Question 31

Default Forward Delay timer

Answer 31

15 seconds

Question 32

Feature that allows a switch to immediately transition from blocking to forwarding, bypassing listening and learning states.

Answer 32

PortFast

Question 33

feature helps defeat these kinds of problems by disabling a port if any BPDUs are received on the port.

Answer 33

BPDU Guard

Question 34

Two components of the Bridge ID that affect whether a switch will be elected root

Answer 34

Lowest priority and if that ties, the lowest MAC address

Question 35

messages which switches use to | exchange information with each other.

Answer 35

bridge protocol data units (BPDU),

Question 36

Global configuration command to set the STP | mode.

Answer 36

spanning-tree mode {pvst | | rapid-pvst | mst}

Question 37

Global configuration command that changes this switch to the root switch. The switch’s priority is changed to the lower of either 24,576 or 4096 less than the priority of the current root bridge when the command was issued.

Answer 37

spanning-tree vlan [vlan-number] root primary

Question 38

Global configuration command that changes the bridge priority of this switch for the specified VLAN.

Answer 38

spanning-tree vlan [vlan-id] priority [priority value}

Question 39

Interface subcommand that changes the STP cost to | the configured value.

Answer 39

spanning-tree vlan [vlan-number] cost [cost value]

Question 40

Interface subcommand that changes the STP port priority in that VLAN (0 to 240, in increments of 16).

Answer 40

spanning-tree vlan [vlan-number] port-priority [priority]

Question 41

Interface subcommand that enables EtherChannel | on the interface.

Answer 41

channel-group [channel-group number] mode {auto | desirable | active | passive | on}

Question 42

Interface subcommand that enables PortFast on the | interface.

Answer 42

spanning-tree portfast

Question 43

Interface subcommand that enables BPDU Guard on | an interface.

Answer 43

spanning-tree bpduguard enable

Question 44

Global command that changes the switch default for PortFast on access interfaces from disabled to enabled.

Answer 44

spanning-tree portfast default

Question 45

Global command that changes the switch default for BPDU Guard on access interfaces from disabled to enabled.

Answer 45

spanning-tree portfast bpduguard default

Question 46

Global command that changes the global setting for | PortFast to disabled.

Answer 46

no spanning-tree portfast default

Question 47

Global command that changes the global setting for | BPDU Guard to disabled.

Answer 47

no spanning-tree portfast bpduguard default

Question 48

Interface subcommand that disables PortFast on the | interface.

Answer 48

spanning-tree portfast disable

Question 49

Interface subcommand that disables BPDU Guard | on an interface.

Answer 49

spanning-tree bpduguard disable

Question 50

Lists details about the state of STP on the | switch, including the state of each port.

Answer 50

show spanning-tree

Question 51

Lists STP information only for the specified | port.

Answer 51

show spanning-tree interface [interface id]

Question 52

Lists STP information for the specified VLAN

Answer 52

show spanning-tree vlan vlan-id

Question 53

Lists information about each VLAN’s root or for | just the specified VLAN.

Answer 53

show spanning-tree [vlan vlan-id] root

Question 54

Lists STP information about the local switch for | each VLAN or for just the specified VLAN

Answer 54

show spanning-tree [vlan vlan-id] | bridge

Question 55

Lists global STP settings for a switch, including the default PortFast and BPDU Guard settings, and the VLANs for which this switch is the root switch

Answer 55

show spanning-tree summary

Question 56

Causes the switch to provide informational | messages about changes in the STP topology

Answer 56

debug spanning-tree events

Question 57

Lists a one-line status message about PortFast on | the listed interface.

Answer 57

show spanning-tree interface [type/number ] portfast

Question 58

Lists information about the state of | EtherChannels on this switch.

Answer 58

show etherchannel [channel-group number] | {brief | detail | port | portchannel | summary}