ccnp sw ch 14

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ccnp sw ch 14
2013-10-22 04:52:15

ch 14
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  1. For a catalyst switch to offer PoE to a device, what must occur?

    a. Nothing, power is always enabled on a port.
    b. The switch must detect that the device needs inline power.
    c. The device muse send a CDP message asking for power.
    d. The switch is configured to turn on power to the port.
  2. Which one of these commands can enable PoE to a switch interface?

    a. inline power enable
    b. inline power on
    c. power inline on
    d. power inline auto
  3. What does a Cisdo IP phone contain to allow it to pass both voice and data packets?

    a. an internal Ethernet hub
    b. an internal 2 port switch
    c. an internal 3 port switch
    d. an internal 4 port switch

    3 links total -  PC (data), Internal to phone (VOIP), and link to the switch.
  4. How can voice traffic be kept separate from any other data traffic theough an IP Phone?

    a. Voice and data travel over separate links.
    b. A special-case 802.1Q trunk is used to connect to the switch.
    c. Voice and data can't be separated, they must intermingle on te link.
    d. Voice and data packets both are encapsulated over an ISL trunk.
  5. What cmd configures an IP phone to use VLAN 9 for voice traffic?

    a. switchport voice vlan 9
    b. switchport voice-vlan 9
    c. switchport voice 9
    d. switchport voip 9
  6. What is the default voice VLAN confition for a switch port?

    a. switchport voice vlan 1
    b. switchport voice vlan dot1p
    c. switchport voice vlan untagged
    d. switchport voice vlan none
  7. If the following interface config cmds have been used, what VLAN numbers will the voice and data be carried over respectfully?

    int gi 1/0/1
    switchport access vlan 10
    switchport trunk native vlan 20
    switchport voice vlan 50
    switchport mode access

    a. vlan 50, vlan 20
    b. vlan 50, vlan1
    c. vlan1, vlan50
    d. vlan20, vlan 50
    e. vlan 50, vlan10
  8. What command can verify the voice VLAN used by a Cisco IP phone?

    a. show cdp neighbor
    b. show interface switchport
    c. show vlan
    d. show trunk
  9. When a PC is connected to the PC switch port on an IP phone, how is QoS trust handled?

    a. The IP phone always trusts the class of service (COS) info coming from the PC.
    b. the IP phone never trusts the PC and always overwrites the CoS bits.
    c. QoS trust for the PC data is handled at the Catalyst switch port, not the IP phone.
    d. the Catalyst switch instructs the IP phone how to trust the PC QoS information.
  10. An IP phone should mark all incoming traffic from an attached PC to have CoS 1.  Complete the following switch command to make that happen:

    switchport priority extend ____

    a. untrusted
    b. 1
    c. cos 1
    d. overwrite 1
  11. What command can verify the PoE status of each switch port?

    a. show inline power
    b. show power inline
    c. show interface
    d. show running-config
  12. Which DSCP codepoint name usually is used for time-critical packets containing voice data?

    a. 7
    b. Critical
    c. AF
    d. EF
  13. What are the 5 power classes for IEEE standards?
    • class     maxpwr @ 48DC
    • 0           15.4 W
    • 1           4.0 W
    • 2           7.0 W
    • 3           15.4 W
    • 4           up to 50 W   (802.3at)
  14. What are the commands to configure PoE?
    • G int fa 0/1
    • I  power inline auto   (or)
    • I  power inline auto max <milliwatts>  (or)
    • I  power inline static (or)
    • I  power inline static max <milliwatts> (or)
    • I power inline never

    • verify with:
    • show power inline
    • show power inline fa 0/1
  15. What are the 4 ways that voice traffic can be sent to the switch?
    1. vlan-id,   separate vlan (vlan-id), pc data is untagged (native vlan),  Trunk 802.1Q -- CoS 802.1p

    2. dot1p,  voice vlan is vlan 0, pc data is untagged (native vlan),  Trunk 802.1Q -- CoS 802.1p

    3. untagged,  voice and pc data both use native vlan (untagged),  Trunk 802.1Q -- CoS 802.1p

    4. none,  voice and pc data both use native vlan (untagged),  no CoS  (default mode)

    • verify with:
    • show interface switchport
    • show interface fa 0/1 switchport
    • show spanning-tree int fa 0/1
  16. What are the 3 basic degradations to voice traffic?
    Delay -  aka latency

    Jitter -  variations in the amount of delay

    Loss - loss of packets in transit
  17. what are the 3 basic types of QoS?
    Best-effort delivery

    Integrated services model (intserv)

    Differentiated services model (diffserv)
  18. describe best effort QoS.
    no real QoS, just the routers and switches doing their job passing data.  No head of the line.
  19. Describe intserv QoS.
    uses a pre-arranged path using RSVP (Resource Reservation Protocol).

    note:  does not scale well for large networks.  Path reservations can quickly overwhelm available bandwidth.
  20. Describe diffserve QoS.
    Applies QoS to each packet on a per hop basis. 

    this is a distributed model where each switch and router handles packets according to their configuration.
  21. describe layer 2 QoS.
    Layer 2 is basically not QoS capable, but, trunking adds a vlan tag, which also has a Class Of Service (CoS) field. 

    When the trunked packet is unencapsulated, the CoS marking is lost.
  22. describe the 2 trunking encapsulations and how they handle COS.
    IEE 8025.1Q - User field contains 3 802.1p bits for CoS.  0-7 (0=low).  Native vlans are not encaped so no COS available.

    Inter-Switch Link (ISL) - 4 bit user filed.  lower 3 bits are for CoS.  Catalyst switches can put 802.1Q CoS values into ISL seamlessly.
  23. Layer 3 QoS with DSCP.  Difference between TOS and QOS.
    ToS - type of service.  3 bits.  aka IP Prec.

    QoS - Quality of service.  6 bits.  DSCP.

    DSCP  Differentiated Services Code Point
  24. Describe DSCP to IP Prec class names.
    class 0  default class,  best effort.

    classes 1-4  Assured Forwarding,  Higher AF numbers = higher pri.  eachclass is sub-divided into 1-low, 2-med and 3-high.   (example AF21 = Assured Forwarding class 2, medium)

    Class 5 - Express forwarding.  For time critical data like VoIP.

    Classes 6-7 -  internetwork control and network control.  Routing overhead, STP, etc.
  25. Define a trust boundary.
    a perimeter formed by switches that do not trust QoS.  usually at the access-layer switches. 

    the trust boundary allows switches to blindly trust QoS markings if they are inside the boundary. 

    PCs are usually untrusted.

    IP phones can be trusted, but not the PC attached to them. 

    By letting the IP phone inside the fence, the switch has less processing to do, it just passes on to the next switch the trusted (QoS marked) packet.
  26. Describe cmds to enable QoS on the switch for IP phones.
    • G mls qos
    • G int fa 0/1
    • I  mls qos trust {qos | ip-prec | dscp}
    • I mls qos trust device cisco-phone
    • I switchport pri extend {cos <value> | trust}

    note:  cos value - ip phone would overwrite cos number in packet from pc to 0.  trust parameter would allow pc to mark cos packets and the IP phone would not change it.
  27. What cmd would configure an uplink port to be trusted, as long as they are inside the QoS fence?
    • G int fa 0/1
    • I  mls qos trust cos
  28. Detail cmds that allow auto QoS.
    • G int fa 0/1
    • I  auto qos voip {cisco-phone | cisco=softphone | trust}

    note, this is a macro that runs many lines of cmds.  use "debug auto qos" to watch
  29. How do you verify voice QoS?  (what cmds)
    show mls qos int fa 0/1

    show int fa 0/1 switchport

    sh run int fa 0/1

    sh auto qos int fa 0/1