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CCNP Encor 350-401 > Chapter 2: Spanning Tree > Flashcards

Chapter 2: Spanning Tree Flashcards

1
Q

List the 802.1D port states

A 
Disabled
Blocking
Listening
Learning
Forwarding
Broken
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2
Q

Identify the CST port state:

-The port is shutdown.

A

Disabled

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3
Q

Identify the CST port state:

  • Port is enabled but not forwarding traffic.
  • Can only receive BPDU from other switches.
A

Blocking

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4
Q

Identify the CST port state:

  • Port has transitioned from a blocking state and can now send or receive BPDUs.
  • Port is capable of becoming root port.
  • 15 seconds.
A

Listening

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5
Q

Identify the CST port state:

  • Port can modify MAC address table with any traffic it receives.
  • Does not forward traffic except BPDUs.
  • 15 seconds
A

Learning

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6
Q

Identify the CST port state:

  • Port can forward all network traffic and update MAC address table.
  • This is the final port state.
A

Forwarding

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7
Q

Identify the CST port state:

  • A configuration or an operational problem on a port that can have major effects has been detected.
  • The port discards packets as long as the problem continues to exist.
A

Broken

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8
Q

By default, how long does 802.1D take for a port to transition through all the port states?

A

30 seconds

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9
Q

List the 802.1D port types

A

Root port
Designated port
Blocking port

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10
Q

Original STP from IEEE.

Ensures loop-free topology for one vlan.

A

802.1D

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11
Q

Root of the spanning-tree from which all path calculations are directed towards.

Lowest BID

A

Root bridge

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12
Q

What is a BPDU?

A

Bridge Protocol Data Unit

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13
Q

What destination MAC does a BPDU use?

A

Multicast 01:80:c2:00:00:00

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14
Q

What does the configuration BPDU identify?

A

Root bridge
Root ports
Designated ports
Blocking ports

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15
Q

When is a Topology Change Notifcation (TCN) BPDU sent?

A

When a link status changes.

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16
Q

Combined cost for a specific path toward the root switch.

A

Root path cost

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17
Q

4-bit value that identifies the preference for a switch to be root bridge.

A

System priority (Bridge priority)

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18
Q

What is the default system priority?

A

32768

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19
Q

What is the system ID extension?

A

12-bit value.

Indicates the VLAN that the BPDU correlates to.

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20
Q

What combines to form the root bridge identifier?

A

Root bridge system MAC
System ID extension
System priority of the root bridge

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21
Q

What combine to form the local bridge identifier?

A

Local switch’s MAC address
System ID extension
System priority of root bridge

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22
Q

The maximum length of time that passes before a bridge port saves its BPDU information.

A

Max age

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23
Q

Max age default value

A

20 seconds

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24
Q

What three timers does STP use to make sure that a network converges properly before a bridging loop occurs?

A

Hello timer
Forward delay
Max age

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25
Q

What are the 2 spanning-tree cost modes?

A

Short mode

Long mode

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26
Q 
STP Port Costs:
10 Mbps
100 Mbps
1 Gbps
10 Gbps
A 
SM / LM
10 Mbps  = 100 / 2,000,000
100 Mbps = 19 / 200,000
1 Gbps = 4 / 20,000 
10 Gbps = 2 / 2,000
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27
Q

Hello timer default interval

A

2 seconds

28
Q

Max age default time

A

20 seconds

29
Q

Forward delay default value

A

15 seconds

30
Q

What command is used to configure spanning-tree for long-mode interface cost?

A

spanning-tree pathcost method long

31
Q

What does a BID consist of?

A 
Bridge priority (system priority)- 2 bytes
MAC address- 6 bytes
32
Q

How many bytes make up a BID?

A

8 bytes

33
Q

Bridge priority range and default value?

A

Range: 0-65535
Default: 32768 (0x8000)

34
Q

Explain the root bridge election process.

A
  1. Switches send out BPDUs with a root BID equal to its own BID and a sender BID that is it’s own BID.
  2. Received BPDUs are analyzed to determine if it is a better BPDU.
  3. The switch that sent the better BPDU becomes the root bridge.
  4. Non-root bridges update their BPDU to advertise the net root BID and root path cost.
35
Q

What determines the root bridge?

A
  1. Lower Bridge priority.

2. Lower MAC address (if priority is the same).

36
Q

Interface STP cost is used to determine ____ ____ ___ ?

A

Root path cost

37
Q

Which switch will become the root bridge?

Switch A:
System priority 16572
MAC 0062.ec9d.c500

Switch B:
System Priority 20480
MAC 0062.ec9d.3500

Switch C:
System priority 32768
MAC 0062.ec9d.a500

A

Switch B.

38
Q

What command is used to display the root bridge?

A

show spanning-tree root

39
Q

Root port election process

A
  1. Interface with lowest path cost.
  2. Interface with the lowest system priority of advertising switch.
  3. Interface with the lowest MAC address of advertising switch.
  4. Lowest port priority, if multiple links involved.
  5. Lower port number, if multiple links involved.
40
Q

If two non-root switches are connected on their designate ports, what port state will one of the ports become?

A

Blocking

41
Q

What determines which port becomes blocked between two non-root switches?

A

Switch must be a designated port

  1. Switch with the higher path cost blocks.
  2. Higher system priority blocks.
  3. Higher MAC address blocks.
42
Q

List the various STP versions.

A 
802.1D
PVST
PVST+
802.1W RSTP
802.1S MST
43
Q

What 3 STP modes do Cisco Catalyst switches operate in?

A

PVST+
RSTP
MST

44
Q

What port types are expected on Catalyst switches?

A

P2P

P2P Edge

45
Q

This type of port specifies portfast is enable on the port.

A

P2P Edge

46
Q

This port type connects with another network device,

A

P2P

47
Q

‘show spanning-tree’ is issued on a switch. The Type field shows *TYPE_INC. What does this signify?

A

Port configuration mismatch between the switch and the switch it’s connected to.

48
Q

True or False:

BPDUs always flow from the edge switches to the root bridge in a stable L2 topology.

A

False.

BPDUs originate from the root bridge.

49
Q

True or False:

Root bridges contain root ports.

A

False:

All ports on a root bridge are designated ports.

50
Q

What cause a TCN BPDU to be generated?

A

L2 topology change.

51
Q

What does the root bridge do when a TCN BPDU is received?

A
  1. Creates a new configuration BPDU.
  2. Sets the topology change flag.
  3. Floods the BPDU to all switches.
52
Q

What does a non-root bridge do when it receives a configuration BPDU with the topology change flag set?

A
  1. Changes MAC address timer to the forwarding delay timer.
  2. Flushes all learned MAC address, EXCEPT MACs that are actively communication.
  3. Reset MAC address timer to default (300 seconds) when second configuration BPDU is received.
53
Q

True or False:

TCNs are generated on a VLAN basis.

A

True

54
Q

What command shows topology changes?

A

show spanning-tree [vlan #] detail

55
Q

True or False:

A root bridge can generate a configuration BPDU with the Topology Change flag set, without ever receiving a TCN.

A

True

56
Q

What are the IEEE spanning-tree versions?

A
  1. 1D Common Spanning Tree
  2. 1W RSTP
  3. 1S MSTP
57
Q

What are the Cisco spanning-tree versions?

A

PVST
PVST+
RPVST+

58
Q

What are the 802.1W port states?

A

Discarding
Learning
Forwarding

59
Q

Name the 802.1W root ports.

A

Root port
Designated port
Alternate port
Backup port

60
Q

Name the 802.1W port types.

A

Edge port
Root port
Point-to-point port

61
Q

True or False:

802.1D improve 802.1W by reducing the number of port states a port transitions through to reach the forwarding state.

A

False

  1. 1D is CST.
  2. W is RSTP
62
Q

A port that connects to the root switch or an upstream switch. Has the best path cost toward the root bridge.

A

Root port

63
Q

A port that provides connectivity to downstream switches and devices.

A

Designated port

64
Q

A port that provides alternate connectivity toward the root through a different switch.

A

Alternate port

65
Q

This port only exists when there are multiple links between the same switches. It cannot guarantee connectivity to the root in the event that the upstream switch fails.

A

Backup port

66
Q

A port where host connect to the L2 topology with one interface and cannot form a loop.

A

Edge port

CCNP Encor 350-401 (10 decks)

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