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31 Days to CCNA > Day 25 - STP (Spanning Tree Protocol) > Flashcards

Day 25 - STP (Spanning Tree Protocol) Flashcards

1
Q

This original IEEE standard allowed for only one instance of STP to run for an entire switched network

A

IEEE STP 802.1D

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2
Q

STP helps prevent __________ in a redundant switched network

A

Loops

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3
Q

Without STP, redundancy in a switched network can introduce what types of issues?

A

Broadcast storms
Multiple frame transmission
MAC database instability

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4
Q

STP creates a __________ that ensures that only one path exists for each network segment at any one time

A

Tree

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5
Q

For any interfaces not chosen to be in a forwarding state, STP places the interfaces into a __________ __________

A

Blocking state

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6
Q

Switches exchange STP configuration every ___ seconds, by default

A

2

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7
Q

The configuration messages exchanged every 2 seconds (by default) are using what protocol and also, what are these messages called?

A

Multicast
BDPUs (Bridge Protocol Data Units)

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8
Q

True or False: Blocked ports listen for BPDUs to listen for whether or not the other side of link is down

A

True

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9
Q

What does the Bridge ID (BID) consist of?

A

Priority value
Bridge MAC address

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10
Q

What is the default bridge priority value?

A

32768

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11
Q

The __________ __________ is the bridge with the lowest BID

A

Root bridge

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12
Q

If the BID default priority value isn’t changed, the switch with the lowest __________ becomes the root bridge

A

MAC address

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13
Q

This is the process by which switches collectively realize that something has changed in the LAN topology

A

STP convergence

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14
Q

What are the 4 steps for STP convergence?

A

Elect a root bridge
Elect root ports
Elect designated ports
Root ports and designated ports transition to forwarding and the other ports transition to blocking

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15
Q

What is the IEEE cost in STP for a 10 Mbps link?

A

100

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16
Q

What is the IEEE cost in STP for a 100 Mbps link?

A

19

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17
Q

What is the IEEE cost in STP for a 1 Gbps link?

A

4

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18
Q

What is the IEEE cost in STP for a 10 Gbps link?

A

2

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19
Q

What four states does STP use?

A

Blocking
Listening
Learning
Forwarding

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20
Q

What is the fifth state that STP uses when a network admin manually disables the port or when a security violation occurs?

A

Disabled

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21
Q

Solve for definition:

The original specification of __________ defined as 802.1D

A

STP

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22
Q

Solve for definition:

Cisco’s enhancement of STP that provides a separate 802.1D spanning tree instance for each VLAN configured in the network

A

PVST+

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23
Q

Solve for definition:

This is 802.1w. It’s an evolution of STP that provides faster convergence. However, it still provides for only a single instance of STP

A

RSTP

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24
Q

Solve for definition:

A Cisco enhancement of RSTP. Provides a separate instance of 802.1w per VLAN

A

RPVST+

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25
Q

PVST+’s tree calculation is for All VLANs or Per VLAN?

A

Per VLAN

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26
Q

STP’s tree calculation is for All VLANs OR Per VLAN?

A

All VLANs

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27
Q

RPVST+’s tree calculation is for All VLANs for Per VLAN?

A

Per VLAN

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28
Q

What STP operation is the default on all Cisco Catalyst switches?

A

PVST+

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29
Q

Switched networks running PVST+ have what characteristics?

A

Per VLAN configuration allows redundant links to be fully utilized

Each additional spanning tree instance for a VLAN adds more CPU cycles to all switches on the network

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30
Q

True or False:

Ports in a blocking state can still receive and process BPDUs

A

True

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31
Q

True or False:

Ports in a listening state can forward data frames received on the interface

A

False

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32
Q

True or False:

Ports in a listening state can learn MAC addresses

A

False

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33
Q

True or False:

Ports in a learning state can receive and process BDPUs

A

True

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34
Q

True or False:

Ports in a learning state can forward data frames switched or received on the interface

A

False

35
Q

True or False:

Ports in a forwarding state can forward data frame switched from another interface or received on the interface

A

True

36
Q

PVST+ requires what for each VLAN?

A

A separate instance of spanning tree

37
Q

In PVST+ the extended Bridge ID with System ID equals what?

A

VLAN identifier in the bridge ID

38
Q

In a PVST+ BID, what 3 fields are included?

A

Bridge priority
Extended system ID (VLAN)
MAC address

39
Q

In RPVST+ a single instance of __________ runs for each VLAN

A

RSTP

40
Q

With RSTP, IEEE improved the convergence performance of STP from 50 seconds to less than ____________

A

10 seconds

41
Q

With RSTP, what is the blocking state called?

A

Discarding state

42
Q

Solve for definition:

A single port on each nonroot switch in which the switch hears the best BPDU out of all the received BPDUs

A

Root port

43
Q

Solve for definition:

Of all switch ports on all switches attached to the same segment/collision domain, this is the port that advertises the best BPDU

A

Designated port

44
Q

Solve for definition:

An RSTP role for a port on a switch that receives a suboptimal BPDU

A

Alternate port

45
Q

RSTP edge (portfast) ports should immediately transition to a __________ __________, thereby skipping 802.1D listening and learning port state

A

Forwarding state

46
Q

Portfast links must be what kind of links?

A

Point to point links with an end device

47
Q

What is the default hello time for PVST+

A

2 seconds

48
Q

What is maximum aging time for PVST+

A

20 seconds

49
Q

What two configuration options will help you achieve load balancing with PVST+

A

Bridge ID manipulation
Port cost manipulation

50
Q

What commands would you use to change the bridge ID for VLAN 1?

A

spanning-tree vlan 1 root primary (or secondary)

spanning-tree vlan 1 priority (priority)

51
Q

The primary keyword in an stp configuration automatically sets the bridge priority value to what?

A

24576

52
Q

The secondary keyword in an stp configuration automatically sets the bridge priority value to what?

A

28672

53
Q

The bridge priority value goes up in increments of what?

A

4096

54
Q

Alternatively, what commands would you use to manually alter the cost of bridge ID priority values?

A

spanning-tree vlan 1 priority 24576

55
Q

What command would you use to verify spanning tree protocol?

A

show spanning-tree

56
Q

What commands would you use to configure portfast and BPDU guard on Fa0/1?

A

int fa0/1
sw mode acc
spanning-tree portfast
spanning-tree bdpuguard enable

57
Q

What can the Bridge Priority range be?

A

0-65535 but in reality it’s only 0-61440 because it goes in increments of 4096

58
Q

What is a Root Bridge elected based on?

A

Bridge ID values (MAC Address and Bridge Priority Value)

59
Q

True or False: When a switch calculates its best path towards the Root Bridge, higher bandwidth links are preferred?

A

True

60
Q

True or False: If a switch has multiple equal cost paths towards the Root Bridge, it will select the neighbor switch with the lowest Bridge ID?

A

True. It will select it based on the lowest MAC Address or a lower assigned Bridge Priority value

61
Q

Ports on the neighbor switch opposite the root port are called what?

A

Designated Ports

62
Q

Root Ports point toward what?

A

Root Bridge

63
Q

The Root Ports and Designated Ports are the most direct path(s) to this?

A

Root Bridge

64
Q

What IEEE standard is MSTP (Multiple Spanning Tree Protocol)?

A

802.1s

65
Q

Does PVST+ allow load balancing?

A

Yes

66
Q

If you had 20 VLANS on a switch running RPVST+ how many Spanning Tree instances would be running?

A
  1. One for each VLAN
67
Q

PVST+ will assign the _____, ______ or _______ role to ports?

A

Root, Designated or Alternate

68
Q

What is the Short-Mode Cost (IEEE) of 20 Gbps?

A

1

69
Q

What is the command to verify Spanning Tree for VLAN 1?

A

show spanning-tree vlan 1

70
Q

On a show spanning tree command, what is the Root ID section telling you about?

A

Tells you about the Root Bridge, which might not necessarily be the switch you’re looking at the output on

71
Q

On a show spanning tree command, what is the Bridge ID section telling you about?

A

This is actually giving you information about the switch you’re running the command on

72
Q

If you entered a Priority value of 5000 what would happen?

A

It would error out since it’s not an increment of 4096

73
Q

If a portfast port has been errdisabled by receiving BPDUs what should you do to bring it back?

A

First, correct the issue
then:
shut
no shut

74
Q

If you had two switches - one primary and one secondary what command could you use to make sure no other switch ever got introduced that had a superior priority value and thus became the root bridge?

A

int {int}
spanning-tree guard root

75
Q

Switch port enters the __________ state at time of election process, when a switch receives a BPDU on a port that indicates a better path to the Root Switch or if a port is not a Root Port.

A

Blocking

76
Q

________ state is the first transitional state after blocking state.

A

Listening

77
Q

This state of an STP port does not participate in any operation of STP because it is considered non-operational.

A

Disabled

78
Q

Switch port enters __________ state after passing through all the states involved in creation of network topology.

A

Forwarding

79
Q

Where would you enable Root Guard?

A

Use Root Guard only on uplink ports that connect to switches or devices that should never become the root bridge. These are typically connections to distribution or core switches.

80
Q

What STP priority setting is NOT permitted on a Cisco switch?

1
0
4096
32768
28672

A

1 because it’s not an increment of 4096

81
Q

How is a root bridge elected when there are multiple switches with a default configuration?

switch with highest priority
switch with lowest priority
switch with lowest MAC address
switch with highest MAC address

A

switch with lowest MAC address

82
Q

Which of these MAC addresses would be chosen in the case of default config on multiple switches?

00:1A:2B:3C:4D:5E
A1:B2:C3:D4:E5:F6
08:00:27:00:FF:AA
2C:33:7F:9A:BC:DE

A

00:1A:2B:3C:4D:5E

83
Q

What two features of the Spanning-Tree Protocol contribute to the time it takes for a switched network to converge after a topology change occurs? (Choose two.)

The max-age timer
The spanning-tree hold down timer
The forward delay
The spanning-tree path cost

A

Max-Age Timer
Forward Delay

84
Q

What three link types have been defined for Rapid Spanning-Tree Protocol? (Choose three.)

Shared
End-to-end
Edge-type
Boundary-type
Point-to-point

A

Shared
Edge-Type
Point-to-Point

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