CLCOR Media And Qos Practice Test 1 — 15 Questions

Question 1

Which command allows an administrator to view the current status of registered media resources, such as transcoders, on a Cisco IOS gateway?

Accepted Answer

show sccp. The `show sccp` command on a Cisco IOS gateway displays the status of SCCP (Skinny Client Control Protocol) clients, which includes registered media resources such as transcoders, conference bridges, and MTPs. These resources register with the gateway's SCCP application, and the output lists their state (e.g., active, idle) and capabilities. This is the correct command to verify that transcoders are registered and available for use.

Answer

show dial-peer voice

Answer

show media resources

Answer

show voice gateway status

Question 2

In a Cisco Collaboration environment, what is the purpose of the 'Media Termination Point' (MTP) in relation to call signaling?

Accepted Answer

To provide DTMF interworking between endpoints.. The Media Termination Point (MTP) in Cisco Collaboration is specifically designed to provide DTMF interworking between endpoints that use different DTMF transport methods (e.g., inband vs. out-of-band). It can also be used for supplementary services like call hold, but its primary purpose in the context of call signaling is to ensure DTMF digits are correctly relayed. Unlike transcoders, MTPs do not change the codec; they only manipulate the media stream for DTMF and other signaling events.

Answer

To limit the bandwidth consumed by a call.

Answer

To provide codec transcoding services.

Answer

To cache video streams for faster playback.

Question 3

You are configuring a Media Resource Group List (MRGL) in CUCM to allow for transcoding. A call is placed between two endpoints where one supports G.711 and the other only supports G.729. If the MRGL contains a Transcoder, what must be configured to ensure the call succeeds?

Accepted Answer

Configure a Transcoder profile on the IOS gateway and assign it to the device pool's MRGL.. To make a G.711-to-G.729 call succeed, you must configure a transcoder on the IOS gateway and associate it with the device pool's Media Resource Group List so CUCM can allocate it for the call. The transcoder performs the actual codec conversion between the two endpoints. Simply enabling a service parameter or setting a region codec does not provision the hardware resource.

Answer

Set the Region codec to 'G.711 to G.729' explicitly.

Answer

Enable 'Allow Transcoding' in the Service Parameters.

Answer

Configure the IOS gateway as a Media Termination Point (MTP) only.

Question 4

You are configuring a Cisco IOS router to perform QoS marking for voice traffic originating from a local PBX. You need to ensure that the voice traffic is marked as DSCP EF. Which configuration command correctly applies this in a policy-map?

Accepted Answer

set dscp 46. The 'set dscp ef' command within a policy-map class is the correct method for modifying the DSCP value of a matching traffic class.

Answer

set ip dscp ef

Answer

mark dscp 46

Answer

set dscp voice

Question 5

You are troubleshooting a scenario where video quality is degrading during periods of high data utilization. You identify that video traffic is being dropped in the network. What is the most likely cause if you are using CBWFQ?

Accepted Answer

Video is not being correctly classified into the priority queue. In CBWFQ, video traffic is placed into a class-based queue, not the priority queue (LLQ). If video is not correctly classified into the priority queue (or a dedicated low-latency queue), it competes with other traffic and can be dropped during congestion. CBWFQ provides fair queuing among classes but does not guarantee low latency unless LLQ is configured. The most likely cause is misclassification or absence of a priority queue for video.

Answer

The voice traffic is taking up all bandwidth

Answer

The router's CPU is overloaded

Answer

The interface is configured for full-duplex

Question 6

You are configuring a Cisco gateway to handle voice traffic. You need to ensure that the gateway trusts DSCP markings from the incoming IP phone. Which command is used on the interface?

Accepted Answer

qos trust dscp. The 'qos trust dscp' command on the interface configures the switch to trust the DSCP values received from the connected device.

Answer

priority trust dscp

Answer

trust dscp

Answer

mls qos trust dscp

Question 7

Which parameter in the CUCM 'Service Parameters' section controls the default region bandwidth for audio calls?

Accepted Answer

Region configuration. CUCM doesn't use a single service parameter for this; instead, it uses the Region configuration to define bandwidth between locations.

Answer

Audio Bandwidth Parameter

Answer

Maximum Audio Bitrate

Answer

System-wide QoS policy

Question 8

When configuring a policy-map for voice traffic, which command is used to assign a specific bandwidth guarantee to a class?

Accepted Answer

bandwidth [kbps]. The command 'bandwidth [kbps]' is used in a policy-map class to assign a specific bandwidth guarantee to that class. It reserves a minimum amount of bandwidth for the class, ensuring that voice traffic gets the required capacity. This is a standard QoS configuration in Cisco IOS.

Answer

rate-limit [kbps]

Answer

guarantee [kbps]

Answer

priority bandwidth

Question 9

Which TWO of the following are key components of the Cisco QoS model for Voice?

Accepted Answer

Classification and Marking. Classification and Marking (A) is a foundational component of the Cisco QoS model for Voice because voice traffic must first be identified (e.g., via NBAR, ACLs, or DSCP/CoS matching) and tagged with the appropriate per-hop behavior such as EF (DSCP 46) so downstream devices can treat it with the required priority. Low Latency Queuing (B) is also a key component, as LLQ provides a strict-priority queue with a configured bandwidth guarantee (e.g., 'priority percent 30' or 'priority 512') that bounds jitter and latency for voice RTP streams while still allowing other classes to be serviced. Best effort queuing (C) is not part of the voice QoS model because it offers no differentiation or delay guarantees, which is unsuitable for voice. Strict Priority Queuing without bandwidth limits (D) is incorrect because an unbounded PQ queue can starve all other traffic; LLQ was specifically created to add a policed bandwidth cap to strict priority for voice. Weighted Random Early Detection (E) is a congestion-avoidance mechanism typically applied to TCP-based data classes, not a core component of the voice QoS model, since voice uses UDP and requires priority queuing rather than drop-based congestion avoidance.

Answer

Best effort queuing

Answer

Strict Priority Queuing (PQ) without bandwidth limits

Answer

Weighted Random Early Detection (WRED)

Question 10

Which TWO of the following are true regarding Cisco Unified Communications Manager (CUCM) Locations?

Accepted Answer

They manage both audio and video bandwidth. Locations manage bandwidth for both audio and video, and they operate independently of regions.

Answer

They are optional for all deployments

Answer

They are used to define codec preferences

Answer

They define the gatekeeper address

Question 11

Which TWO of the following are examples of call signaling protocols that require specific QoS treatment?

Accepted Answer

H.323. SIP and H.323 are the primary signaling protocols used in CUCM and require CS3 marking.

Answer

RTCP

Answer

RTP

Answer

SCCP

Question 12

A collaboration engineer is configuring a Cisco IOS XE router to mark voice and video traffic at the network edge. The router connects to a service provider that trusts DSCP markings. The engineer must ensure that voice bearer traffic is marked EF, call signaling is marked CS3, and video conferencing traffic is marked AF41. Which two configurations are required to accomplish this marking on the router? (Choose two.)

Accepted Answer

Create a class-map that matches voice bearer traffic using a match protocol or ACL, and then in a policy-map, set the DSCP value to ef for that class.. To mark voice bearer as EF, you need a class-map to identify the traffic and a policy-map to set the DSCP value. Applying the policy-map inbound on the edge router ensures packets are marked before entering the service provider network. The other options either use incorrect tools for marking or omit required traffic types. Thus, the two correct configurations are the ones that classify and mark voice bearer and apply the policy inbound.

Answer

Use the set ip dscp ef command in a route-map and apply it to the WAN interface outbound to mark voice traffic.

Answer

Configure a policy-map that sets DSCP to af41 for video traffic and cs3 for call signaling, and attach it to the ingress interface with service-policy input.

Answer

Configure the mls qos trust dscp command on the ingress interface to trust incoming DSCP markings from the IP phone.

Question 13

A network administrator is configuring a Cisco IOS router to support a SIP trunk to a Cisco Unified Communications Manager. The administrator wants to ensure that voice signaling traffic is marked with the correct DSCP value. Which DSCP value is recommended for call signaling traffic in a Cisco collaboration network?

Accepted Answer

CS3 (24). Call signaling traffic should be marked with CS3 (DSCP 24) to ensure it receives appropriate priority without competing with voice media. This is a Cisco best practice and is widely adopted in collaboration deployments. Signaling must be reliable but is not as delay-sensitive as voice media, so a lower DSCP than EF is used.

Answer

AF31 (26)

Answer

EF (46)

Answer

AF41 (34)

Question 14

A network engineer is deploying a new branch with a Cisco IOS XE router acting as the WAN edge. The service provider marks all traffic with DSCP 0 (Best Effort), so the engineer must remark voice RTP flows entering the LAN-side interface before they are queued on the WAN interface. The engineer wants to identify voice bearer traffic by its DSCP value rather than by ACL. Which class-map match statement accomplishes this on the ingress interface?

Accepted Answer

match ip dscp ef. A class-map that matches the EF DSCP value selects traffic the phones already mark as voice bearer, satisfying the requirement to classify by marking instead of ACL. This is the standard approach when the trust boundary is moved to a routed interface: the router recognizes the existing Layer 3 marking, then the policy-map can preserve, remark, or queue those packets appropriately toward the WAN.

Answer

match protocol rtp audio

Answer

match cos 5

Answer

match access-group name VOICE-ACL

Question 15

A collaboration engineer is troubleshooting poor voice quality on a Cisco IP Phone. The network uses a Cisco Catalyst switch with QoS enabled. The engineer suspects that the phone's voice traffic is not being marked correctly. Which command on the switch can verify the DSCP value of voice packets received from the phone?

Accepted Answer

show mls qos ip. To verify the DSCP value of voice packets received from a phone, the show mls qos ip command on a Cisco Catalyst switch provides a breakdown of packets by DSCP. This helps confirm that the phone is marking voice media as EF and that the switch is trusting or re-marking appropriately.

Answer

show interfaces

Answer

show policy-map interface

Answer

show mls qos interface