CCNP: Building Multilayer Switched Networks Chapter 7

Module 7 Exam
Module 7 ‐ 1 ‐
1. What two traffic types must be included when calculating the bandwidth requirements to
support a voice stream in an IP telephony network? (Choose two.)
· voice queues
· voice carrier stream (*)
· voice management traffic
· voice services traffic
· call control signalling (*)
· routing updates
2. Which three statements are true concerning basic Quality of Service (QoS) regarding the
support of Cisco IP phones? (Choose three.)
· Critical traffic may take possession of a resource by dropping low‐priority packets. (*)
· If network management indicates that specific traffic is experiencing latency, jitter, and
packet loss, then QoS can be used to adjust how that traffic is handled. (*)
· Priority access into the core layer is provided based on Layer 3 QoS tags. (*)
· Priority traffic marking occurs at the core layer using Layer 3 QoS tags.
· Jitter is the amount of time that a packet resides in the output queue of an interface.
· Best practices for QoS trust boundaries include marking traffic as far away from the
traffic source as possible.
3. Which four devices must be included in power requirement calculations for UPS backup of a
VoIP environment? (Choose four.)
· switches forwarding VoIP traffic, but not providing power to IP phones (*)
· switches forwarding VoIP traffic and providing power to IP phones (*)
· Internet gateways
· IP phones (*)
· CallManager servers (*)
· Internet firewalls
4. What happens when untrusted traffic enters a trust boundary device?
· Traffic is sent unmarked.
· Traffic is marked with the default QoS value.
· Traffic is marked with the new QoS value appropriate for the policy in place. (*)
· Traffic is sent and the original QoS value is retained.
5. When Cisco IOS is being used in a switched environment, which two statements are true
about configuring AutoQoS? (Choose two.)
· Once AutoQoS is configured, manual adjustments to the QoS settings cannot be done
unless AutoQoS is disabled with the no auto qos command.
· The command auto qos voip cisco‐phone should be configured on switch ports
connected to end‐user devices. (*)
· The command auto qos voip cisco‐phone should be configured on trunk links between
switches.
· The global configuration command auto qos voip trust must be configured before
configuring interfaces with the auto qos voip cisco‐phone command.
· The mls qos global configuration command must be configured before configuring
interfaces with the auto qos voip cisco‐phone command.
· When configuring the auto qos voip cisco‐phone command on interfaces, it is
important that CDP be enabled. (*)
Module 7 Exam
Module 7 ‐ 2 ‐
6. What are three characteristics of voice traffic? (Choose three.)
· For reasonable voice quality, there cannot be any packet loss.
· For voice quality, delay should be no more than 45 ms round trip.
· For voice quality, delay should be no more than 150 ms one way. (*)
· TCP is used to package voice packets.
· UDP is used to package voice packets. (*)
· Voice packets are typically small ‐ usually 60 to 120 bytes. (*)
7. Refer to the exhibit. PC data traffic and IP phone packet data share the same physical link to
the switch and the same switch port. What should be done to prevent the sound quality of
the voice traffic from deterioration when data is sent on the same link?
· Configure the trust boundaries of the network at the switch access port.
· Configure the trust boundary of the network on the IP phone.
· Enable the voice VLAN feature on the switch access ports to carry IP voice traffic from
the IP phone. (*)
· Enable QoS on the switch by entering the mls qos global configuration command.
· Configure the MAC address of the IP phone as a static secure or sticky secure MAC
addresses on the switch access port.
8. Which two statements are true about voice traffic in a converged network? (Choose two.)
· Voice traffic is the only traffic type that requires QoS functionality.
· Because of the available bandwidth, separating voice traffic from data traffic on the same
VLAN (subnet) is not required.
· Voice traffic tends to require a more consistent amount of bandwidth per conversation
than does data traffic. (*)
· Transaction based traffic tends to have higher QoS requirements than does voice traffic.
· Voice traffic utilizes relatively small packet sizes. (*)
· To reduce processing latency, voice VLANs are implemented to allow voice traffic to be
forwarded without VLAN tags.
9. Which three statements about voice traffic are true? (Choose three.)
· TCP ensures the quality of voice traffic.
· The one‐way delay should be no more than 150 ms. (*)
· Voice packets typically vary between 20 and 60 bytes.
· A typical voice call requires between 17 kbps and 106 kbps. (*)
· A typical voice call requires approximately 150 bps for voice‐control traffic. (*)
· Voice traffic has relatively weak QoS requirements.
Module 7 Exam
Module 7 ‐ 3 ‐
10. Refer to the exhibit. What is the effect on the trust boundary when configuring the command
mls qos trust cos on the switch port that is connected to the IP phone?
· The host is now establishing the CoS value and has effectively become the trust
boundary.
· The switch is rewriting packets it receives from the IP phone and determining the CoS
value.
· Effectively the trust boundary has been moved to the IP phone. (*)
· The switch will no longer tag incoming voice packets and will trust the distribution layer
switch to set the CoS.
11. Refer to the exhibit. Which switch interface configuration command would automatically
configure quality of service (QoS) for voice over IP (VoIP) within a QoS domain?
· mls qos trust
· switchport priority extend cos 7
· switchport priority extend trust
· auto qos voip cisco‐phone (*)
Module 7 Exam
Module 7 ‐ 4 ‐
12. Refer to the exhibit. What is the effect when the switchport priority extend cos 3 command is
configured on the switch port interface connected to the IP phone?
· Effectively, the trust boundary has been moved to the PC attached to the IP phone.
· The IP phone is enabled to override with a CoS value of 3 the existing CoS marking of
the PC attached to the IP phone. (*)
· The computer is now establishing the CoS value and has effectively become the trust
boundary.
· The switch will no longer tag incoming voice packets and will extend the trust boundary
to the distribution layer switch.
13. Which statement describes the function of a trust boundary?
· Trust boundaries are a point in the network where decisions about CoS markings on
incoming packets are made. (*)
· Trust boundaries determine whether certain types of traffic can pass.
· Trust boundaries are a point in the network where QoS functionality begins and ends.
· Trust boundaries are points in the network where Layer 2 CoS markings are converted to
Layer 3 DSCP or IP precedence markings.