Shared Flashcard Set

Details

CCNP SWITCH 642-813 - Voice and Video
Voice and Video
31
Computer Networking
Professional
07/07/2010

Additional Computer Networking Flashcards

 


 

Cards

Term
How much DC power is applied when using PoE?
Definition
48V DC
Term
What are the two methods for providing PoE to connected devices?
Definition
Cisco Inline Power (ILP), and IEEE 802.3af
Term
How does 802.3af detect if a device needs power?
Definition
It sends a small voltage over the line, and measures the resistance to see if the device is drawing power.
Term
How many classes of power are there in 802.3af? What is the default?
Definition
5 classes (0-4), default is 0 (15.4W)
Term
How does Cisco ILP detect if a device needs power?
Definition
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.
Term
What pins get the power in PoE?
Definition
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)
Term
What is the best way that a switch can detect power requirements to a phone when running ILP?
Definition
By exchanging CDP information.
Term
When using the command "show inline power" a class of 'n/a' means what?
Definition
That the switch is providing power with ILP, and NOT 802.3af.
Term
What does 'power inline never' do?
Definition
Disables PoE on that port.
Term
How many ports on a Cisco IP phone's internal switch?
Definition
3! Upload, PC, and phone!
Term
What are the four trunking methods with a Cisco IP Phone?
Definition
VLAN-configured, dot1p, untagged, none.
Term
When using dot1p to trunk a Cisco IP Phone, what VLAN is voice data sent on?
Definition
VLAN 0
Term
What is the only difference if trunking an IP phone with 'untagged' or 'none'?
Definition
Untagged placed the voice/data information on the NATIVE VLAN. None placed the voice/data information on the Access VLAN.
Term
Define Delay, latency, jitter, and loss.
Definition
-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.
Term
What are the three basic types of QoS?
Definition
Best Effort, Integrated services, and Differentiated services.
Term
QoS must be implemented where on the network to be totally effective?
Definition
on EVERY device that connects sender to receiver.
Term
What is Best-Effort delivery?
Definition
First In First Out, packets are sent in the order that they are received.
Term
What is Integrated Services Delivery?
Definition
Establishing a dedicated path through the network before any data is sent. Think of this as circuit switching over a packet switched network.
Term
What is Differentiated Services Delivery?
Definition
Applying QoS on a per-flow and per-hop basis for all packets.
Term
Layer 2 devices can only utilize what one of the three basic QoS methods?
Definition
Best Effort Delivery.
Term
How many bits are used to classify layer 3 traffic when using ToS, and how many when using DSCP?
Definition
-ToS=3bits
-DSCP=6bits
Term
What is the range for IP precedence QoS values, what do they mean, and what is the default Class value?
Definition
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).
Term
What are the three levels of Drop Precedence in DSCP? Which one gives better service?
Definition
Low, Medium, High. Lower is better.
Term
Typically, when should an organization trust QoS parameters, and when should it NOT?
Definition
Trust when it is generated within your own network, and do NOT trust at the boundary with any external organization.
Term
What is a QoS trust boundary?
Definition
The perimeter formed by switches that do NOT trust incoming QoS.
Term
How does the command 'mls qos' affect the way a switch trusts QoS markers?
Definition
Without it, the switch trusts everything. With it, the switch trusts NOTHING!
Term
Using the 'mls qos trust' command what are the tree things that can be trusted? what is generally used on IP phones?
Definition
cos, ip-precedence, or DSCP. cos is used for IP Phones.
Term
At what layer should Auto-QoS be used?
Definition
the access layer, or wherever you have more QoS leveraging services (like IP phones!)
Term
What command will automatically trust QoS information received on a trunk?
Definition
mls qos trust cos.
Term
What are the tree types of Auto-QoS options for voice?
Definition
Cisco-phone, Cisco-softphone, and trust (used for trunks/uplinks!)
Term
If a port is not trusted in QoS, what happens to the voice packet QoS when they hit the switch?
Definition
They are overwritten by the switch! (bad!)
Supporting users have an ad free experience!