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ICND 2 > Spanning Tree Protocol > Flashcards

Spanning Tree Protocol Flashcards

1
Q

What is one benefit of PVST+

  • PVST+ reduces the CPU cycles for all switches in the network
  • PVST+ automatically selects the root bridge location, to provide optimization
  • PVST+ allows the root switch location to be optimized per vlan
  • PVST+ supports Layer 3 load balancing without loops
A

PVST+ allows the root switch location to be optimized per vlan

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2
Q

Which three statements about RSTP are true? (Choose three)

  • RSTP significantly reduces topology reconvening time after a link failure
  • RSTP expands the STP port roles by adding the alternate and backup roles
  • RSTP port states are blocking, discarding, learning, or forwarding
  • RSTP provides a faster transition to the forwarding state on point-to-point links than STP does
  • RSTP also uses the STP proposal-agreement sequence
  • RSTP uses the same timer based process as STP on point-to-point links
A

RSTP significantly reduces topology reconvening time after a link failure

RSTP expands the STP port roles by adding the alternate and backup roles

RSTP provides a faster transition to the forwarding state on point-to-point links than STP does

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3
Q

Which two states are the port states when RSTP has converged? (Choose two)

blocking

learning

disabled

forwarding

listening

A

blocking

forwarding

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4
Q

Which option describes how a switch in rapid PVST+ mode responds to a topology change?

  • It immediately deletes dynamic MAC addresses that were learned by all ports on the switch
  • It sets a timer to delete all MAC addresses that were learned dynamically by ports in the same STP instance
  • It sets a timer to delete dynamic MAC addresses that were learned by all ports on the switch
  • It immediately deletes all MAC addresses that were learned dynamically by ports in the same STP instance
A

It immediately deletes all MAC addresses that were learned dynamically by ports in the same STP instance

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5
Q

Which spanning tree feature places a port immediately into a forwarding state?

BPDU guard

PortFast

loop guard

UDLD

UplinkFast

A

PortFast

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6
Q

Which process is associated with spanning-tree convergence?

determining path cost

electing designated ports

learning the sender bridge ID

assigning the port ID

A

electing designated ports

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7
Q

Which IEEE standard does PVST+ use to tunnel information?

  1. 1x
  2. 1q
  3. 1w
  4. 1s
A

802.1q

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8
Q

Which term describes a spanning-tree network that has all switch ports in either the blocking or fowarding state?

A

converged

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9
Q

Refer to the exhibit. The output that is shown is generated at a switch. Which three statements are true? (Choose three.)

A. All ports will be in a state of discarding, learning, or forwarding.
B. Thirty VLANs have been configured on this switch.
C. The bridge priority is lower than the default value for spanning tree.
D. All interfaces that are shown are on shared media.
E. All designated ports are in a forwarding state.
F. This switch must be the root bridge for all VLANs on this switch.

A

A. All ports will be in a state of discarding, learning, or forwarding.

C. The bridge priority is lower than the default value for spanning tree.

E. All designated ports are in a forwarding state.

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10
Q

What is one benefit of PVST+?

A. PVST+ supports Layer 3 load balancing without loops.
B. PVST+ reduces the CPU cycles for all the switches in the network.
C. PVST+ allows the root switch location to be optimized per VLAN.
D. PVST+ automatically selects the root bridge location, to provide optimized bandwidth usage.

A

C. PVST+ allows the root switch location to be optimized per VLAN.

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11
Q

Which three statements about RSTP are true? (Choose three.)

A. RSTP significantly reduces topology reconverging time after a link failure.
B. RSTP expands the STP port roles by adding the alternate and backup roles.
C. RSTP port states are blocking, discarding, learning, or forwarding.
D. RSTP provides a faster transition to the forwarding state on point-to-point links than STP does.
E. RSTP also uses the STP proposal-agreement sequence.
F. RSTP uses the same timer-based process as STP on point-to-point links.

A

A. RSTP significantly reduces topology reconverging time after a link failure.

B. RSTP expands the STP port roles by adding the alternate and backup roles.

D. RSTP provides a faster transition to the forwarding state on point-to-point links than STP does.

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12
Q

Which two states are the port states when RSTP has converged? (Choose two.)

A. discarding
B. listening
C. learning
D. forwarding
E. disabled

A

A. discarding

D. forwarding

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13
Q

Refer to the exhibit. Each of these four switches has been configured with a hostname, as well as being configured to run RSTP. No other configuration changes have been made. Which three of these show the correct RSTP port roles for the indicated switches and interfaces? (Choose three.)

A. SwitchA, Fa0/2, designated
B. SwitchA, Fa0/1, root
C. SwitchB, Gi0/2, root
D. SwitchB, Gi0/1, designated
E. SwitchC, Fa0/2, root
F. SwitchD, Gi0/2, root

A

A. SwitchA, Fa0/2, designated

B. SwitchA, Fa0/1, root

F. SwitchD, Gi0/2, root

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14
Q

Which port state is introduced by Rapid-PVST?

A. learning
B. listening
C. discarding
D. forwarding

A

C. discarding

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15
Q

Which two of these statements regarding RSTP are correct? (Choose two.)

A. RSTP cannot operate with PVST+.
B. RSTP defines new port roles.
C. RSTP defines no new port states.
D. RSTP is a proprietary implementation of IEEE 802.1D STP.
E. RSTP is compatible with the original IEEE 802.1D STP.

A

B. RSTP defines new port roles.

E. RSTP is compatible with the original IEEE 802.1D STP.

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16
Q

Refer to the exhibit. Which switch provides the spanning-tree designated port role for the network segment that services the printers?

A. Switch1
B. Switch2
C. Switch3
D. Switch4

A

C. Switch3

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17
Q

Refer to the exhibit. At the end of an RSTP election process, which access layer switch port will assume the discarding role?

A. Switch3, port fa0/1
B. Switch3, port fa0/12
C. Switch4, port fa0/11
D. Switch4, port fa0/2
E. Switch3, port Gi0/1
F. Switch3, port Gi0/2

A

C. Switch4, port fa0/11

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18
Q

Refer to the exhibit. Why has this switch not been elected the root bridge for VLAN1?

A. It has more than one interface that is connected to the root network segment.
B. It is running RSTP while the elected root bridge is running 802.1d spanning tree.
C. It has a higher MAC address than the elected root bridge.
D. It has a higher bridge ID than the elected root bridge.

A

D. It has a higher bridge ID than the elected root bridge.

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19
Q

Refer to the topology shown in the exhibit. Which ports will be STP designated ports if all the links are operating at the same bandwidth? (Choose three.)

A. Switch A – Fa0/0
B. Switch A – Fa0/1
C. Switch B – Fa0/0
D. Switch B – Fa0/1
E. Switch C – Fa0/0
F. Switch C – Fa0/1

A

B. Switch A – Fa0/1
C. Switch B – Fa0/0
D. Switch B – Fa0/1

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20
Q

In which circumstance are multiple copies of the same unicast frame likely to be transmitted in a switched LAN?

A. during high traffic periods
B. after broken links are re-established
C. when upper-layer protocols require high reliability
D. in an improperly implemented redundant topology
E. when a dual ring topology is in use

A

D. in an improperly implemented redundant topology

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21
Q

Which two switch states are valid for 802.1w? (Choose two.)

A. listening
B. backup
C. disabled
D. learning
E. discarding

A

D. learning
E. discarding

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22
Q

Which option describes how a switch in rapid PVST+ mode responds to a topology change?

A. It immediately deletes dynamic MAC addresses that were learned by all ports on the switch.
B. It sets a timer to delete all MAC addresses that were learned dynamically by ports in the same STP instance.
C. It sets a timer to delete dynamic MAC addresses that were learned by all ports on the switch.
D. It immediately deletes all MAC addresses that were learned dynamically by ports in the same STP instance.

A

D. It immediately deletes all MAC addresses that were learned dynamically by ports in the same STP instance.

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23
Q

What does STP prevent in a switched network with redundant paths?

A

loops

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24
Q

What feature of PVST+ is not available in RSTP?

A

per-VLAN STP instance

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25
Q

What is the sequence of spanning-tree initialization?

A

blocking, listening, learning, forwarding

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26
Q

Which item represents a problem that is solved by PortFast?

DHCP Timeout

Bandwidth

Throttling

Duplex Mismatch

Native VLAN Mismatch

A

DHCP Timeout

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27
Q

What two symptoms indicate that a loop might exist in the network?

CPU load of switches approaches 100 percent

MAC addresses flap frequently between ports of switches

Expired messages are received by the hosts

The load on the WAN links in the network approaches 100 percent utilization

A

CPU load of switches approaches 100 percent

MAC addresses flap frequently between ports of switches

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28
Q

Which BID would win election as the root, assuming that the switches with these BIDs were in the same network?

32769: 0200.1111.1111
32769: 0200.2222.2222
4097: 0200.1111.1111
4097: 0200.2222.2222

A

4097:0200.1111.1111

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29
Q

All switches operate as the ____ switch when they boot up.

A

root

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30
Q

When an access port is enabled with the PortFast feature, which two STP states are bypassed?

A

learning

listening

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31
Q

How does STP prevent forwarding loops at OSI Layer 2?

A

port blocking

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32
Q

The switchport with the best path to the root bridge and exists only on non-root bridges. Only one is allowed per bridge

A

root port

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33
Q

This port exists on root and non-root bridges. All switchports on the root bridge are designated as this. Only one allowed per segment.

A

designated port

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34
Q

What port on a non-root bridge receives and forwards frames towards the root bridge as needed. If multiple switches exist on the same segment, an election process determines the designated switch, and the corresponding switch port begins forwarding frames for the segment.

A

designated port

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35
Q

What port does not forward (blocks) data frames and is not populating the MAC address table with the source addresses of frames that are seen on that segment?

A

Nondesignated port

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36
Q

What STP switchport is shutdown?

A

disabled port

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37
Q

What is the STP port cost of a 10 Mbps link?

A

100

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38
Q

What is the STP port cost of a 100 Mbps link?

A

19

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39
Q

What is the STP port cost of a 1 Gbps link?

A

4

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40
Q

What is the STP port cost of a 10 Gbps link?

A

2

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41
Q

The root bridge becomes the switch with the lowest ____?

A

BID

42
Q

What three items make up the BID?

A

bridge priority

MAC address

Extended System ID

43
Q

What is the default spanning tree configuration for Cisco Catalyst switches?

A

PVST+

44
Q

What is the default value of the bridge priority number?

A

32768

45
Q

The bridge ID is in increments of?

A

4096

46
Q

If all priority numbers are the same value, what is used as a tie breaker to determine the root bridge?

A

Lowest MAC Address

47
Q

What command allows you to change the cost of the connection?

A

spanning-tree cost [#]

48
Q

If there are multiple links between switches with equal cost, what is used to determine the root port?

A

Port ID

49
Q

What command allows you to change the port priority? Note: The priority can be changed in increments of 16

A

spanning-tree port-priority

50
Q

If one of the links between two switches fail, the blocking port will remain in the blocking state of ____ seconds.

A

20

51
Q

During the blocking state, the switch will wait for a BPDU. It will then move into the listening state for ____ seconds.

A

15

52
Q

A switchport will transition from the listening state to the learning state for ____ seconds.

A

15

53
Q

The port will transition from the learning state to the forwarding state and will become the _____ port.

A

root

54
Q

What command would allow you to configure SW1 as the root bridge for VLAN 1?

A

spanning-tree vlan 1 root primary

55
Q

What command would allow you to configure SW2 as the backup root bridge for VLAN 1 in case SW1 fails?

A

spanning-tree vlan 1 root secondary

56
Q

If the root path cost and received BID values are the same, the port with the _____ port ID is selected as the root port

A

lowest

57
Q

What is the IEEE standard for STP

A

802.1D

58
Q

Is spanning tree enabled by default?

A

Yes

59
Q

What command is used to verify the root bridge?

A

show spanning-tree vlan

60
Q

If BPDU Guard is enabled, what happens to the port if it receives a BPDU

A

shuts it down

61
Q

PortFast should only be configured on what type of port?

A

access

62
Q

What commands are used to enable PortFast on all nontrunking interfaces and enable BPDU guard globally for all PortFast-enabled ports?

A

spanning-tree portfast default

spanning-tree portfast bpdu guard default

63
Q

What commands are used to configure BPDU guard and PortFast on an interface?

A

spanning-tree portfast

spanning-tree bpdu guard enable

64
Q

When PortFast feature is enabled globally, what command is used to verify?

A

show spanning-tree summary

65
Q

With STP, what type of failure is more disruptive? Forwarding or blocking

A

Forwarding

66
Q

What is the IEEE standard for RSTP?

A

802.1w

67
Q

In Rapid PVST+, what port is a backup to the root port?

A

alternate port

68
Q

In Rapid PVST + what port is a backup to the designated port?

A

backup port

69
Q

What RPVST+ link type interconnects two device with full duplex

A

point to point

70
Q

What RPVST+ link type has a connected port is running half duplex, typically seen when a switch is connected to a hub

A

Shared link

71
Q

What RPVST+ link type has a connected port that is not connected to another switch or hub but connects to an endpoint?

A

Edge port

72
Q

What type of trunking encapsulation must be used with PVST?

A

ISL (Cisco proprietary)

73
Q

Which of the following is not detected as a topology change by RSTP?

A switch in the topology is powered off

A port moves to the blocking state

A new primary root bridge is manually configured

A non-edge root port moves to the forwarding state

A

A port moves to the blocking state

74
Q

What feature prevents non designated ports from inadvertently forming bridging loops if the steady flow of BPDUs is interrupted? It puts the ports into the loop-inconsistent state, which keeps the port in a blocking state

A

loop guard

75
Q

What commands automatically recovers a err-disabled port from BPDU guard?

A

errdisable recovery cause bpduguard

err disable recovery interval [interval]

76
Q

Once an STP-enabled network has converged, what are the valid port states for participating switch ports?

A

blocking

forwarding

77
Q

When RPVST+ detects a topology change, what does it do?

A

Floods BPDUs with TC flag set to all affected ports

78
Q

You issue the spanning-tree root command on a switch port that you are connecting to a new, unconfigured switch. What are you most likely attempting to do?

A

prevent the new switch from being elected root

79
Q

What feature places inconsistent ports into the blocking state and prevents a switchport from transitioning to the forwarding state when it stops receiving BPDUs?

A

loop guard

80
Q

What are the three RPVST states will a switchport will pass through when it is turned on

A

Discarding

Learning

Forwarding

81
Q

What two commands allow you to enable Rapid Spanning Tree Protocol (RSTP)?

A

spanning-tree mode mst

spanning-tree mode rapid-pvst

82
Q

What is the standard number for RSTP, which includes PortFast, UplinkFast, and BackboneFast.

A

802.1w

83
Q

What does PVST + do if it detects a topology change?

A

Sends TCN to instance root bridge, which floods BDPUs with TC flag set to other ports within the instance

84
Q

When a topology change occurs and the root bridge sends out BPDUs with the TC flag set to switches in the PVST+ instance, what do the switches do?

A

Reduce their bridging table aging timers to the value of the forward delay. When aging time expires, the switch will flush its MAC addresses

85
Q

If a topology change occurs using the Rapid-PVST+ what MAC addresses are flushed?

A

MAC addresses of affected ports in the affected VLAN

86
Q

In Rapid-PVST+ protocol, the detecting port of the topology change will flood BPDUs with the TC flag set until the _____ timer on that port expires.

A

While

87
Q

What is the value of the While timer?

A

Twice the hello time for the affected port

88
Q

What happens when the While timer runs out on a Rapid-PVST+ port?

A

MAC addresses on affected ports are flushed

89
Q

How long does Rapid-PVST+ take to converge?

A

Less than 10 seconds

90
Q

If a switch port determines at any time during the STP state process that a switching loop would be caused by entering the forwarding state, the switch port will enter what state, in which the switch receives BPDUs but does not direct them to the system module?

A

error-disabled

91
Q

When the loop guard feature is enabled and the port stops receiving BPDUs, loop guard puts the port into the loop-inconsistent state, which keeps the port in a _____ state.

A

blocking

92
Q

After the port starts receiving BPDUs again, what does loop-guard automatically do?

A

re-enables the port so that it transitions through the normal STP states

93
Q

What command enables loop guard for the entire switch?

What command enables loop guard for specific ports?

A

spanning-tree loopguard default

spanning-tree guard loop

94
Q

Used to prevent newly introduced switches from being elected as the new root switch. It gives administrators the ability to maintain control over which switch is the root

A

Root guard

95
Q

How is root guard applied and what command allows you to do this?

A

per-port basis

spanning-tree guard root

96
Q

What happens if root guard is enabled on a loop guard-enabled port?

A

loop guard is automatically disabled

97
Q

What command is used to enable Multiple Spanning Tree, which uses RSTP to enable multiple spanning trees for groups of one or more VLANs?

A

spanning-tree mode mst

98
Q

When the topology changes, if an interface that was blocking needs to move to a forwarding state, the time spent in the listening state is defined by what?

A

Forward delay timer

99
Q

If an interface was in a forwarding state, and it does not need to change to blocking, what happens to that interface?

A

stays in forwarding state

100
Q

What command enables RSTP on a switch?

A

spanning-tree mode rapid-pvst

ICND 2 (16 decks)

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