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myccnp switch 300-115 > Voice and Video > Flashcards

Voice and Video Flashcards

1
Q

source

A

http://www.coursehero.com/flashcards/430780/CCNP-SWITCH-642-813-Voice-and-Video/

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2
Q

What command will automatically trust QoS information received on a trunk?

A

mls qos trust cos.

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3
Q

How many ports on a Cisco IP phone’s internal switch?

A

3! Upload, PC, and phone!

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4
Q

Layer 2 devices can only utilize what one of the three basic QoS methods?

A

Best Effort Delivery.

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5
Q

When using the command “show inline power” a class of ‘n/a’ means what?

A

That the switch is providing power with ILP, and NOT 802.3af.

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6
Q

What is Differentiated Services Delivery?

A

Applying QoS on a per-flow and per-hop basis for all packets.

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7
Q

How does Cisco ILP detect if a device needs power?

A

The switch sends a tone along the line, and since Cisco IP Phones auto-loopback their interfaces when powered off, the switch will ‘hear’ the tone when it is sent back.

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8
Q

How much DC power is applied when using PoE?

A

48V DC

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9
Q

What is Integrated Services Delivery?

A

Establishing a dedicated path through the network before any data is sent. Think of this as circuit switching over a packet switched network.

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10
Q

How many classes of power are there in 802.3af? What is the default?

A

5 classes (0-4), default is 0 (15.4W)

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11
Q

When using dot1p to trunk a Cisco IP Phone, what VLAN is voice data sent on?

A

VLAN 0

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12
Q

What are the tree types of Auto-QoS options for voice?

A

Cisco-phone, Cisco-softphone, and trust (used for trunks/uplinks!)

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13
Q

Using the ‘mls qos trust’ command what are the tree things that can be trusted? what is generally used on IP phones?

A

cos, ip-precedence, or DSCP. cos is used for IP Phones.

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14
Q

If a port is not trusted in QoS, what happens to the voice packet QoS when they hit the switch?

A

They are overwritten by the switch! (bad!)

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15
Q

How does the command ‘mls qos’ affect the way a switch trusts QoS markers?

A

Without it, the switch trusts everything. With it, the switch trusts NOTHING!

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16
Q

Typically, when should an organization trust QoS parameters, and when should it NOT?

A

Trust when it is generated within your own network, and do NOT trust at the boundary with any external organization.

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17
Q

What is the best way that a switch can detect power requirements to a phone when running ILP?

A

By exchanging CDP information.

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18
Q

At what layer should Auto-QoS be used?

A

the access layer, or wherever you have more QoS leveraging services (like IP phones!)

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19
Q

What is a QoS trust boundary?

A

The perimeter formed by switches that do NOT trust incoming QoS.

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20
Q

What does ‘power inline never’ do?

A

Disables PoE on that port.

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21
Q

How many bits are used to classify layer 3 traffic when using ToS, and how many when using DSCP?

A

-ToS=3bits-DSCP=6bits

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22
Q

What pins get the power in PoE?

A

Both methods send power over pairs 2 and 3 (pins 1,2 and 3,6) but 802.3af can also send on the other pairs (pins 4,5 and 7,8)

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23
Q

What are the four trunking methods with a Cisco IP Phone?

A

VLAN-configured, dot1p, untagged, none.

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24
Q

What are the three levels of Drop Precedence in DSCP? Which one gives better service?

A

Low, Medium, High. Lower is better.

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25
Q

What are the two methods for providing PoE to connected devices?

A

Cisco Inline Power (ILP), and IEEE 802.3af

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26
Q

What are the three basic types of QoS?

A

Best Effort, Integrated services, and Differentiated services.

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27
Q

What is the only difference if trunking an IP phone with ‘untagged’ or ‘none’?

A

Untagged placed the voice/data information on the NATIVE VLAN. None placed the voice/data information on the Access VLAN.

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28
Q

How does 802.3af detect if a device needs power?

A

It sends a small voltage over the line, and measures the resistance to see if the device is drawing power.

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29
Q

QoS must be implemented where on the network to be totally effective?

A

on EVERY device that connects sender to receiver.

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30
Q

Define Delay, latency, jitter, and loss.

A

-Delay is the time it takes a device to process data. -Latency is the total end-to-end delay time. -Jitter is the variance in end-to-end delay. -loss is the measure of packets that were not delivered to the destination.

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31
Q

What is the range for IP precedence QoS values, what do they mean, and what is the default Class value?

A

0-7, default is 0 (best effort), 1-4 are Assured Forwarding (AF), 5 is Express Forwarding (EF), and 6-7 are for network information (routing protocols and STP).

32
Q

What is Best-Effort delivery?

A

First In First Out, packets are sent in the order that they are received.

33
Q

How does a Cisco IP phone connect upstream?

A

via an 802.1Q trunk or a single VLAN access port

34
Q

What are the 2 choices for VLANs with IPT?

A

they must be carried over a voice VLAN (VVID) or over a regular data VLAN (ie. The native VLAN or the PVID)

35
Q

How is the IPT 802.1 trunk negotiated?

A

Automatically using DTP and CDP

36
Q

How does IPT behave when the voice VLAN is in vlan-id mode?

A

data goes over native vlan, voice goes over specified VLAN, voice QOS is 802.1p

37
Q

How does IPT behave when the voice VLAN is in dot1p mode?

A

data goes over native vlan, voice goes over VLAN0, voice QOS is 802.1p

38
Q

How does IPT behave when the voice VLAN is in untagged mode?

A

data and voice over native vlan, no QOS but still uses 802.1p trunk

39
Q

How does IPT behave when the voce VLAN is in the default none mode?

A

data and voice over native vlan no QOS and no 802.1p trunk

40
Q

What is latency?

A

the total delay from start to finish

41
Q

What is jitter?

A

variation in delay

42
Q

What are the three basic types of QOS?

A

best effort delivery, integrated services model, and differentiated services model

43
Q

What is best effort delivery QOS?

A

switches make an effort to move packets as quickly as possible

44
Q

What is integrated services model QOS?

A

A path is pre-arranged for priority along the complete path from source to destination using the RSVP protocol.

45
Q

What is differentiated services model QOS?

A

Each network device handles packets individually with no advance reservations

46
Q

What method of QOS does voice traffic use most frequently?

A

differentiated services

47
Q

How does an L2 switch do QOS?

A

an L2 switch can only forward frames best effort unless going across a trunk

48
Q

How does 802.1q handle COS?

A

The frame tag includes a 3 bit COS value from 0 (low) to 7 (high). Native vlans are untagged so no COS

49
Q

How does ISL handle COS?

A

The frame tag contains a 3 but portion tagged from 0 (low) to 7 (high)

50
Q

How does L3 QOS classification happen?

A

The TOS field in the header is used. 2 methods 3 bits or 6 bits

51
Q

What is DSCP?

A

Differentiated services code point

52
Q

How does DSCP handle IP precedence?

A

5 classes with 3 drop precedences

53
Q

What is DSCP codepoint EF(46)?

A

Critical…used most often for IPT

54
Q

What is DSCP codepoint AF41(34)?

A

Flash override (class 4)

55
Q

What is DSCP codepoint AF31(26)?

A

Flash (class 3)

56
Q

What is DSCP codepoint AF21(18)?

A

immediate (class 2)

57
Q

What is DSCP codepoint AF11(10)?

A

priority (class 1)

58
Q

What is a QoS trust boundary?

A

The point at which a switch decides to trust incoming Qos. Usually at boundary with ISP

59
Q

How is a QoS trust bondary configured?

A

Every switch and router in a network must be configured with appropriate QoS features and policies

60
Q

Where is the QoS trust boundary usually configured on an IP phone?

A

Usually QoS from VOIP but not PC dataa

61
Q

What are the 4 steps to extend QoS trust?

A

1- enable qos, 2-define qos parameters to be trusted, 3-make trust conditional, 4-instruct IP phone how to extnd boundary

62
Q

For QoS, switch uplinks should always be considered as ____ _____?

A

trusted ports

63
Q

How much BW does a PSTN connection use?

A

63 kbps

64
Q

How much BW does a voip connection use?

A

12 kbps with headers and compression

65
Q

How do Cisco IP phones communicate with the CCM?

A

with the skinny protocol

66
Q

What does the skinny protocol do?

A

transmits keystrokes from phone and commands from CCM

67
Q

How do IP phones communicate with each other?

A

Once the CCM gives them the parameters, they use RTP

68
Q

What is RTP?

A

Real-time Transport Protocol

69
Q

Which feature is automatically enabled when a voice VLAN is configured, but not automatically disabled when a voice VLAN is removed?

A

portfast

70
Q

What is a *Voice VLAN*?

A

A Voice VLAN is a VLAN that segregates voice traffic from user data traffic in the same interface. Both the data and voice VLANs must be explicitly configured.

71
Q

What are the two methods IP Phones can use to learn about the *Voice VLAN*?

A

IP Phones can use CDP if Cisco IP Phones or DHCP Option 156 for non-Cisco Phones to learn about the Voice VLAN.

72
Q

What is usually implemented to provide better service for Voice?

A

QoS is usually implemented to prioritize voice traffic over data.

73
Q

What configuration command sets up the Voice VLAN on a port?

A

Switch(config-if)# switchport voice vlan <vlan-id></vlan-id>

74
Q

What issues does Voice QoS solve?

A

Voice QoS solves two major issues.

  • Predictability for voice traffic
  • Jitter and delay
75
Q

What cannot be solved by *Voice QoS*?

A

Voice QoS cannot solve issues caused by chronic congestion, as that implies there is a design problem in the network.

76
Q

What is *Expedited Forwarding*?

A

Expedited Forwarding is a QoS setting that matches against Voice traffic.

myccnp switch 300-115 (73 decks)

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