CLCOR Media And Qos Practice Test 3 — 15 Questions

Question 1

Which feature in CUCM is used to block calls when the available bandwidth in a location is exceeded?

Accepted Answer

Locations CAC. Locations CAC (Call Admission Control) is the correct answer because CUCM uses the Locations configuration to define the maximum bandwidth available between locations and to deny new calls when that bandwidth is exhausted. When a call would exceed the configured audio or video bandwidth for a location pair, CUCM rejects the call with a reorder tone or redirects it to a secondary path if configured. This is the native, built-in CAC mechanism in CUCM.

Answer

Gatekeeper

Answer

Bandwidth Manager

Answer

RSVP

Question 2

What is the primary function of a 'Class Map' in a Cisco IOS QoS configuration?

Accepted Answer

To categorize and match specific traffic flows. A Class Map in Cisco IOS QoS is used to identify and classify traffic by matching criteria such as ACLs, DSCP, CoS, or NBAR protocols. It defines 'what' traffic to match, and is later referenced by a Policy Map that defines the action. This separation of classification (class-map) from action (policy-map) is the foundation of Modular QoS CLI (MQC).

Answer

To define the action taken on traffic

Answer

To set the DSCP value for a packet

Answer

To assign a specific interface for traffic

Question 3

You are observing that video traffic is marked as DSCP 0. How can you fix this at the network level without changing the endpoint configuration?

Accepted Answer

Use an ACL to match the traffic and a policy-map to re-mark it. When video endpoints send DSCP 0 (best-effort), the marking must be corrected in the network path. A class-map matches the traffic (e.g., by ACL identifying RTP/Video over the correct port range), and a policy-map with a set dscp command re-marks it to the desired value such as AF41 for interactive video. Applying this via MQC (Modular QoS CLI) on the ingress interface fixes the marking without touching the endpoint configuration.

Answer

Disable traffic shaping

Answer

Change the interface speed

Answer

Enable auto-qos on the interface

Question 4

Which TWO of the following are considered best practices for implementing QoS in a Cisco collaboration network?

Accepted Answer

Mark traffic as close to the source as possible. Option A is correct because Cisco QoS best practice is to classify and mark traffic as close to the source as possible, typically on the endpoint or the first-hop access switch, so that the DSCP value is preserved end-to-end and every downstream device can apply consistent per-hop behavior without re-classifying. Option D is correct because extending the trust boundary to the access layer switch allows that switch to trust the DSCP markings from Cisco IP phones and other endpoints, enforcing classification at the network edge rather than re-marking later. Option B is wrong because trusting all incoming traffic by default lets users or rogue devices set arbitrary DSCP values, which can abuse priority queues and break QoS guarantees. Option C is wrong because marking only at the WAN edge is too late—traffic has already traversed the LAN unclassified, and the WAN edge cannot reliably distinguish applications after congestion or encryption. Option E is wrong because disabling QoS removes classification, queuing, and policing, which degrades voice and video quality rather than improving performance.

Answer

Trust all incoming traffic by default

Answer

Only mark traffic at the WAN edge

Answer

Disable all QoS policies to improve performance

Question 5

Which statement best describes the difference between policing and shaping?

Accepted Answer

Policing drops traffic, whereas shaping buffers it. Policing and shaping both measure traffic against a configured rate, but they react differently when the rate is exceeded. Policing simply drops (or remarks) packets that exceed the committed rate, making it a hard enforcement mechanism typically applied on ingress. Shaping, on the other hand, buffers excess packets and delays their transmission so they are sent later within the configured rate, smoothing bursts rather than discarding them.

Answer

Policing buffers traffic, whereas shaping drops it

Answer

Both use buffers to manage congestion

Answer

Both are applied only on ingress interfaces

Question 6

Which THREE of the following are valid reasons to use a Media Termination Point (MTP)?

Accepted Answer

Bridging different signaling protocols. Option B is correct because an MTP can bridge different signaling protocols by terminating the signaling and media on each side, allowing calls to interconnect between otherwise incompatible protocol variants. Option C is correct because MTPs enable media anchoring, which is required for features such as call recording, lawful intercept, and certain supplementary services that need the media stream to pass through a controlled point. Option E is correct because MTPs provide DTMF interworking, converting out-of-band DTMF (for example, SIP INFO or H.323) into in-band or RFC 2833 events so that endpoints using different DTMF transport methods can communicate. Option A is not correct because transcoding between G.711 and G.729 is the function of a transcoder (hardware or software DSP resource), not an MTP. Option D is not correct because an MTP does not increase voice bandwidth; it terminates and relays media, and any bandwidth impact would typically be neutral or negative, not an increase.

Answer

Providing transcoding for G.711 to G.729

Answer

Increasing voice bandwidth

Question 7

Which TWO of the following media resource types are supported in CUCM?

Accepted Answer

Media Termination Point (MTP). In Cisco Unified Communications Manager (CUCM), media resource types are configured under Media Resources and include annunciators, conference bridges, Media Termination Points (MTPs), music on hold (MOH) servers, and transcoders. Option C, Media Termination Point (MTP), is correct because an MTP is a software or hardware media resource registered to CUCM that provides supplementary services such as DTMF conversion, RSVP agent functionality, and H.323-to-SIP interworking by terminating and reoriginating media streams. Option E, Transcoder, is correct because a transcoder is a media resource that converts one codec (for example, G.711) to another (for example, G.729) so endpoints with mismatched codecs can communicate. Option A, IP Phone, is incorrect because a phone is an endpoint device, not a media resource type configured under Media Resources. Option B, Dial-Peer, is incorrect because dial peers are configuration elements on IOS voice gateways (used for call routing), not a CUCM media resource type. Option D, Voice Gateway, is incorrect because a voice gateway is a network device that connects CUCM to external networks such as PSTN or other PBXs, not a media resource type within CUCM.

Answer

IP Phone

Answer

Dial-Peer

Answer

Voice Gateway

Question 8

Which THREE of the following are key features provided by a QoS policy-map?

Accepted Answer

Bandwidth reservation. A QoS policy-map is the component that applies actions to traffic classes, and bandwidth reservation (A) is a core action it can enforce, typically via the bandwidth or priority commands to guarantee a minimum or strict-priority share of link capacity. Traffic marking (B) is also a key policy-map action, using commands like set dscp or set cos to rewrite QoS bits so downstream devices can classify and treat packets consistently. Traffic policing (C) is another standard policy-map action, implemented with the police command to meter flows and drop or re-mark packets that exceed a committed rate. The remaining options do not belong: interface IP address assignment (D) is a Layer 3 interface configuration task, not a QoS policy-map function, and dynamic routing updates (E) are handled by routing protocols such as OSPF or EIGRP, not by QoS policy-maps.

Answer

Interface IP address assignment

Answer

Dynamic routing updates

Question 9

Which TWO of the following are common audio codecs used in Cisco collaboration?

Accepted Answer

G.711. G.711 (option B) is a correct answer because it is a standard ITU-T narrowband audio codec (64 kbps PCM, using either A-law or mu-law companding) that is universally supported in Cisco collaboration endpoints and gateways for toll-quality voice. G.729 (option C) is also correct because it is a widely used ITU-T compressed audio codec (8 kbps CS-ACELP) commonly deployed in Cisco voice and collaboration environments to conserve bandwidth on WAN links. Option A (JPEG) is incorrect because it is a still-image compression standard, not an audio codec. Option D (H.264) is incorrect because it is a video compression standard used for video streams, not audio. Option E (MP3) is incorrect because, although it is an audio codec, it is a consumer music format and is not a standard codec used in Cisco collaboration call signaling/media negotiation.

Answer

JPEG

Answer

H.264

Answer

MP3

Question 10

Which THREE of the following factors impact the quality of video calls in a network?

Accepted Answer

Packet loss. Packet loss (A) is correct because dropped RTP/UDP packets in a video stream cause visible artifacts, freezing, and audio gaps, directly degrading call quality. Jitter (C) is correct because variation in packet inter-arrival times disrupts the playout buffer, causing choppy audio and stuttering video even when average delay is acceptable. Latency (E) is correct because high end-to-end delay (typically above 150 ms one-way) impairs interactivity and, combined with jitter and loss, degrades the real-time experience. Interface description (B) is only a text label on an interface and has no effect on traffic handling, and router uptime (D) is an availability metric that does not by itself determine video quality as long as the device is forwarding packets.

Answer

Interface description

Answer

Router uptime

Question 11

A network engineer is deploying a new branch office with a Cisco IOS XE gateway that connects to the service provider via a 100-Mbps Ethernet WAN link. The engineer needs to ensure that interactive voice traffic always receives priority treatment during congestion, while preventing non-real-time traffic from being starved. Which QoS mechanism should be configured on the WAN interface to guarantee strict priority for voice while still servicing other queues?

Accepted Answer

Configure a low-latency queue with the priority command inside a policy-map, and apply it to the WAN interface with service-policy output.. A low-latency queue created with the priority command inside a policy-map provides strict priority scheduling for voice traffic, ensuring that voice packets are always transmitted first when congestion occurs. The priority policer limits the amount of voice traffic that can enter the priority queue, preventing starvation of other queues. This mechanism is the standard way to guarantee voice quality on a WAN interface.

Answer

Enable traffic shaping on the WAN interface to smooth out bursts and reduce congestion for all traffic types.

Answer

Configure weighted random early detection (WRED) on the WAN interface to drop non-voice packets before congestion occurs.

Answer

Apply class-based weighted fair queueing (CBWFQ) with a bandwidth guarantee for the voice class, and rely on the scheduler to prioritize voice.

Question 12

A network engineer is configuring LLQ on a Cisco IOS router to protect voice traffic. The voice class is assigned a priority of 512 kbps. During periods of congestion, which mechanism ensures that voice packets are not delayed by lower-priority traffic?

Accepted Answer

The priority queue is serviced before other queues, and a policer drops packets that exceed the configured rate.. LLQ provides a strict priority queue that is serviced before other queues, ensuring voice packets experience minimal delay and jitter. The built-in policer enforces the configured bandwidth limit, dropping excess packets to prevent the priority queue from consuming all bandwidth and starving other traffic. This dual mechanism makes LLQ ideal for real-time voice.

Answer

Weighted fair queueing allocates bandwidth equally among all flows, including voice.

Answer

Traffic shaping buffers excess voice packets and sends them later.

Answer

The priority queue is serviced only when other queues are empty, but no policer is applied.

Question 13

A collaboration engineer is deploying a new branch office with Cisco Unified Communications Manager and wants to ensure that voice traffic is marked with the appropriate DSCP value. The service provider requires that voice bearer traffic use EF ( Expedited Forwarding). Which DSCP value should be configured on the IP phones for voice media?

Accepted Answer

EF (46). Voice bearer traffic should be marked with EF (Expedited Forwarding, DSCP 46) to ensure low latency, jitter, and loss. This is a standard recommendation and is often required by service providers. The IP phone configuration must set the voice media DSCP to EF, while call signaling typically uses CS3.

Answer

AF41 (34)

Answer

CS3 (24)

Answer

CS5 (40)

Question 14

A network administrator is troubleshooting poor voice quality on a Cisco Unified Communications Manager cluster. The administrator suspects that the issue is related to the Differentiated Services Code Point (DSCP) value being used for voice bearer traffic. Which DSCP value is recommended by Cisco for voice bearer traffic to ensure it receives priority treatment in the network?

Accepted Answer

EF (Expedited Forwarding). Cisco recommends marking voice bearer traffic with EF (Expedited Forwarding), which is DSCP 46. This marking ensures that voice packets are placed in a low-latency queue and receive priority treatment across the network. Other DSCP values like AF31, CS3, and AF41 are used for different traffic types such as call signaling and video, and do not provide the strict priority required for voice.

Answer

CS3 (Class Selector 3)

Answer

AF41 (Assured Forwarding 41)

Answer

AF31 (Assured Forwarding 31)

Question 15

A collaboration engineer is deploying a new branch where WAN congestion causes jitter on voice calls. The carrier marks all traffic with DSCP 0 on ingress. The engineer wants the branch Cisco IOS router to reclassify voice bearer traffic into the EF class and apply priority queueing before the traffic enters the MPLS WAN. Which configuration approach accomplishes this goal?

Accepted Answer

Configure a class-map matching RTP media ports, then a policy-map that uses the priority command, and apply it outbound on the WAN interface with service-policy output.. Because the carrier resets all packets to DSCP 0, the branch router cannot rely on trust. The engineer must classify voice bearer by RTP port range, mark or treat it as EF, and give it strict-priority queueing with the priority command in a policy-map applied outbound on the WAN interface. This restores low-latency treatment toward the congested MPLS path.

Answer

Configure RSVP between the branch router and the WAN headend to reserve bandwidth for voice bearer traffic.

Answer

Configure the WAN interface with mls qos trust dscp and enable auto-qos on the interface.

Answer

Configure a policy-map with a bandwidth guarantee for voice and apply it inbound on the LAN interface.