CCNP switch slides 17

Question 1

source

Answer 1

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

Question 2

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

Answer 2

mls qos trust cos.

Question 3

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

Answer 3

3! Upload, PC, and phone!

Question 4

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

Answer 4

Best Effort Delivery.

Question 5

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

Answer 5

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

Question 6

What is Differentiated Services Delivery?

Answer 6

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

Question 7

How does Cisco ILP detect if a device needs power?

Answer 7

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.

Question 8

How much DC power is applied when using PoE?

Answer 8

48V DC

Question 9

What is Integrated Services Delivery?

Answer 9

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

Question 10

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

Answer 10

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

Question 11

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

Answer 11

VLAN 0

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

They are overwritten by the switch! (bad!)

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

By exchanging CDP information.

Question 18

At what layer should Auto-QoS be used?

Answer 18

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

Question 19

What is a QoS trust boundary?

Answer 19

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

Question 20

What does ‘power inline never’ do?

Answer 20

Disables PoE on that port.

Question 21

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

Answer 21

-ToS=3bits-DSCP=6bits

Question 22

What pins get the power in PoE?

Answer 22

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)

Question 23

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

Answer 23

VLAN-configured, dot1p, untagged, none.

Question 24

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

Answer 24

Low, Medium, High. Lower is better.

Question 25

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

Answer 25

Cisco Inline Power (ILP), and IEEE 802.3af

Question 26

What are the three basic types of QoS?

Answer 26

Best Effort, Integrated services, and Differentiated services.

Question 27

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

Answer 27

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

Question 28

How does 802.3af detect if a device needs power?

Answer 28

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

Question 29

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

Answer 29

on EVERY device that connects sender to receiver.

Question 30

Define Delay, latency, jitter, and loss.

Answer 30

-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.

Question 31

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

Answer 31

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).

Question 32

What is Best-Effort delivery?

Answer 32

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