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CCIE R&S Written > Ethernet, VLANs, and Spanning Tree Protocol > Flashcards

Ethernet, VLANs, and Spanning Tree Protocol Flashcards

0
Q

Which switch port setting will be automatically detected even if auto-negotiation is disabled? What does it use to do this?

A

Speed. The switch uses the incoming electrical signal.

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1
Q

What Cisco switch feature automatically detects crossover and straight-through cables and swaps the pairs its ports use so copper Ethernet works properly?

A

Auto-MDIX

Officially, automatic medium-dependent interface crossover

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2
Q

What function in auto-negotiation does a switch use to determine port speed?

A

Fast Link Pulses

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3
Q

How does a switch choose a duplex setting if auto-negotiation is disabled?

A

It uses the default setting for the port speed.

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4
Q

What is the default duplex setting for:
A) 10BaseT
B) 100BaseT
C) 1000BaseT

A

A) half
B) half
C) full

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5
Q

How can you disable switch port auto-negotiation?

A

Statically configure the port speed and duplex.

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6
Q

What Ethernet port setting uses loopback circuitry?

A

Half duplex

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7
Q

When configuring speed and duplex manually, which must be set first?

A

Speed

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8
Q

Name the two most common forms of Ethernet framing.

A

Ethernet V2 and 802.3.

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9
Q

How can an Ethernet V2 frame indicate the protocol contained within it?

A

Via its Type field.

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10
Q

What are the two ways an 802.3 Ethernet frame can signal what type of traffic is contained within it?

A

An 802.2 (or LLC) field or a SNAP header with a Type field.

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11
Q

What does 802.2 use to announce the traffic type contained within the Ethernet frame?

A

An SSAP and a DSAP.

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12
Q

What makes the bits in an Ethernet address byte different from the rest of the Ethernet frame? Name two terms for this bit setup.

A

The bits move right-to-left in order of significance. This is called canonical or little-endian.

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13
Q

What is the 8th bit in the first byte of an Ethernet address used for? What’s the term for it?

A

It’s used to identify the address as unicast (0) or multicast (1). It’s called the I/G bit.

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14
Q

What’s the 7th bit in the first byte of an Ethernet address used for? What’s the term for it?

A

It identifies whether the address is assigned by the hardware vendor (0) or whether it’s been set by an administrator (1). The term is U/L, for Universal/Local.

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15
Q

What’s the OUI for an Ethernet multicast address?

A

0x01005E

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16
Q

Give the length of a SNAP header and the 802.2 DSAP that signifies it’s there.

A

2 bytes; 0xAA

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17
Q

What’s the IEEE designation for Fast Ethernet?

A

802.3u

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18
Q

What’s the IEEE designation for GigE over fiber?

A

802.3z

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19
Q

What’s the IEEE designation for GigE over copper?

A

802.3ab

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20
Q

What command displays the Ethernet addresses known to a switch?

A

Switch> show mac address-table

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21
Q

Give the maximum distance for 1000BaseLX in each of MM and SM.

A

MM 3 km, SM 10 km

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22
Q

Give the maximum distance for 1000BaseSX in each of 62.5-micron and 50-micron fiber.

A

62.5-micron 220 m, 50-micron 550m

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23
Q

Give the maximum length of 1000BaseZX.

A

100 km

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24
Q

What’s the best practice with respect to VLANs and IP addressing?

A

Maintain a one-to-one relationship between VLANs and IP subnets.

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25
Q

What are the three tasks one can perform in VLAN configuration mode?

A
  1. Create VLANs
  2. Set basic administration parameters
  3. Verify VTP configuration
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26
Q

What VLANs can be configured in VLAN configuration mode?

A

Normal-range VLANs (1-1005)

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27
Q

Where is the VLAN database stored? What’s the filename?

A

Flash; vlan.dat

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28
Q

Give the VLAN configuration mode commands that:

  1. Display the VLANs that are actively configured on the switch.
  2. Display the VLANs that will be in place after configuration changes are finalized.
A
  1. show current

2. show proposed

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29
Q

Give the VLAN configuration mode commands that:

  1. Implement the proposed configuration without leaving VLAN configuration mode.
  2. Cancel changes and leave VLAN configuration mode.
  3. Cancel the changes and stay in VLAN configuration mode.
A
  1. apply
  2. abort
  3. reset
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30
Q

Give the VLAN configuration database command that creates VLAN #15 and titles it cisco.

A

vlan 15 name cisco

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31
Q

Give the command that can be used in interface configuration mode to create VLAN 15 and assign it to the interface.

A

(config-if)# switchport access vlan 15

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32
Q

What distinguishes a primary VLAN from a secondary VLAN in a private VLAN?

A

The primary VLAN is promiscuous; its members can talk to any other member of the private VLAN. Members of a secondary VLAN can talk to each other and to members of the primary VLAN.

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33
Q

Name and briefly describe the two types of secondary VLANs.

A

Community VLANs have multiple members that talk to each other.
Isolated VLANs have a single member that can only communicate with members of the primary VLAN.

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34
Q

Name the three items that VTP advertises about a VLAN.

A
  1. VLAN ID
  2. VLAN name
  3. VLAN type (Ethernet, Token Ring, etc.)
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35
Q

What VTP mode(s) issue(s) advertisements?

A

Server and client

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36
Q

What VTP mode(s) forward(s) received VTP advertisements?

A

Server, client, and transparent

37
Q

What VTP mode(s) allow(s) you to create or modify VLANs using configuration commands?

A

Server and transparent

38
Q

How does a VTP domain track changes to try to ensure that the most current configuration is on each switch?

A

It uses VTP revision numbers.

39
Q

What is the default VTP mode on a switch?

A

Server

40
Q

What causes a switch to start sending VTP updates?

A

When the VTP domain name is set.

41
Q

How could a switch configured as a VTP client inadvertently get the wrong VTP information?

A

It could receive a VTP announcement from the wrong domain first. VTP clients adopt the first VTP domain name they see.

42
Q

A VTP domain should have at least how many VTP servers?

A

2

43
Q

Where do VTP servers store their vlan.dat files? How about VTP clients?

A

Both store the files in flash. (Depending on the model, some can store vlan.dat in NVRAM, too)

44
Q

How can you prevent DoS attacks via VTP?

A

Set a VTP password.

45
Q

What encryption do VTP passwords use?

A

MD5

46
Q

Give the command that sets a switch’s VTP mode to transparent.

A

(config)# vtp mode transparent

47
Q

Give the commands that define a switch’s VTP domain as CCIE-domain and the password as CCIE.

A

(config) # vtp domain CCIE-domain

(config) # vtp password CCIE

48
Q

True or False: VTP domain names are case-sensitive.

A

True

49
Q

What is the range of normal VLAN numbers?

A

1-1001

50
Q

What is the extended range of VLAN numbers?

A

1006-4094

51
Q

What VLAN number is reserved and cannot be used?

A

0

52
Q

What VLAN number range(s) can be pruned by VTP?

A

2-1001

these are also the VLANs that can be advertised

53
Q

Which VLAN mode(s) can use extended VLANs?

A

VTP transparent mode

55
Q

Where does a switch in VTP transparent mode store extended-range VLAN configuration commands?

A

Running configuration only

56
Q

Which VLAN identification method(s) support(s) extended-range VLANs?

A

Both ISL and 802.1Q

57
Q

Which VLAN identification method(s) support(s) the concept of a native VLAN?

A

802.1Q only

58
Q

What concept does ISL use to support trunking?

A

Encapsulation–it puts a new header around data.

59
Q

By how much does ISL increase the size of an Ethernet frame?

A

26 bytes (the size of the header)

60
Q

Looking at a frame on an ISL-trunked link, how could you determine that the frame is using ISL?

A

The frame has a source MAC of the device performing the trunking and a destination MAC of 0100.0C00.0000 or 0300.0C00.0000.

61
Q

Where does a switch in VTP transparent mode store normal-range VLAN information?

A

In both vlan.dat (Flash) and running configuration.

62
Q

How many bytes does 802.1Q add to an Ethernet frame?

A

4

63
Q

How does 802.1Q signal to devices that a tag exists?

A

The first two bytes of the tag are an EtherType of 0x8100.

64
Q

How does the native VLAN option in 802.1Q add resiliency to an Ethernet network?

A

It allows the switch to attempt to continue sending data on the native VLAN even if trunking fails.

65
Q

What is the default DTP mode?

A

Desirable

66
Q

Give the commands that display:

  1. A summary of trunk-related information
  2. Trunking details for interface g0/0
  3. Nontrunking details for interface g0/0
A
  1. show interface trunk
  2. show interface g0/0 trunk
  3. show interface g0/0 switchport
67
Q

What command allows you to administratively forbid VLANs from existing over a trunk?

A

switchport trunk allowed

68
Q

What two conditions must be present for a VLAN to be active on a trunk?

A

It must be allowed on the trunk and configured on the switch.

69
Q

Give the interface configuration commands that tell the switch to do the following:

  1. Always trunk on this end; send DTP to inform the other side.
  2. Don’t send DTP messages.
  3. Initiate DTP conversations and trunk if negotiation succeeds.
  4. Listen for DTP and trunk if negotiation succeeds.
A
  1. switchport mode trunk
  2. switchport nonegotiate
  3. switchport mode dynamic desirable
  4. switchport mode dynamic auto
70
Q

How can routers learn about trunking interfaces?

A

Via manual configuration–there’s no DTP support.

71
Q

Give the command that you’d put on a router sub-interface to indicate that VLAN 201, the VLAN for this sub-interface, is the 802.1Q native VLAN.

A

(config-subif)# encapsulation dot1q 201 native

72
Q

True or False: VTP can pass over a Q-in-Q service, but CDP cannot.

A

False–both can pass over Q-in-Q.

73
Q

Give the three parts of the STP bridge ID in later STP implementations like PVST+ and MST. Give the length of each.

A

Priority: 4 bits
System ID Extension (VLAN ID): 12 bits
System ID (MAC Address): 48 bits

74
Q

What four fields does a switch update in a Hello BPDU from the root bridge before forwarding it out to neighbors?

A

Cost
Bridge ID (puts its own ID in the BPDU)
Port priority
Port number

75
Q

True or False: Bridges forward Hello BPDUs out ports they are blocking so other bridges know they are a potential future path to the root.

A

False

76
Q

List the four items a switch uses to choose its root port by order of relevance.

A
  1. Cost
  2. Lowest forwarding bridge ID
  3. Lowest port priority from the forwarding bridge
  4. Lowest port number from the forwarding bridge
77
Q

What’s the default port priority? How about the range?

A
  1. Range is 0-240 by 16s.
78
Q

How is the designated port for a segment determined?

A

Cost, bridge ID, port priority, port number (same as root port)

79
Q

What are the default STP Hello and Maxage timers?

A

2 seconds and 20 seconds (Maxage is 10x Hello)

80
Q

Under what circumstance does a switch not have to wait for the Maxage timer to expire to declare a link down?

A

When the link is a failed port channel.

81
Q

Give the revised IEEE and 802.1t STP costs, respectively, for the following Ethernet speeds:

  1. 10 Mbps
  2. 100 Mbps
  3. 1 Gbps
  4. 10 Gbps
A
  1. 100; 2,000,000
  2. 19; 200,000
  3. 4; 20,000
  4. 2; 2,000
82
Q

What will a switch that experiences a topology change do? What will other switches do to help out?

A

The switch will send a Topology Change Notification BPDU out its root port. Switches upstream forward the TCN toward the root and send back Hellos with the TCA bit marked.

83
Q

How does a root bridge respond to an advertised change in topology?

A

It sends Hellos marked with TCAs out all ports, ensuring that all switches in the network learn that there has been a topology change.

84
Q

How will a switch that receives a Hello BPDU marked with the TCA bit change its behavior?

A

It will use the Forward Delay timer to age out CAM entries.

85
Q

What is the default for the STP Forward Delay timer?

A

15 seconds

86
Q

What are the transitory STP states?

A

Listening and Learning

88
Q

How does PVST+ differ from traditional STP?

A

It allows for a different root bridge and blocking interfaces per VLAN.

89
Q

How does PVST+ treat non-Cisco switches in an 802.1Q environment? What happens in the non-Cisco switches?

A

It views them as a single link over to Cisco switches on the other side. The non-Cisco switches have a Common Spanning Tree for all VLANs.

90
Q

How do Cisco switches communicate PVST+ information across a non-Cisco switching domain?

A

They set their BPDUs with the multicast destination of 0100.0CCC.CCCD, which the non-Cisco switches see as standard multicast and forward to the other side.

91
Q

Give the switch command that tells you details about the root bridge. What information in the output of this command would tell you that you’re looking at the root bridge?

A

show spanning-tree root

You’re looking at the root bridge if the cost listed is 0.

92
Q

What’s the difference between the STP Listening and Learning states?

A

During the Learning state, the switch learns MAC addresses from received frames.

CCIE R&S Written (2 decks)

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