CLCOR Media And Qos — 25 Questions

Question 1

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?

Choose an answer to begin — your selection is scored in the full session.

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 2

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 3

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 4

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 5

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 6

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. 'show sccp connections' or 'show sccp' is the standard way to verify the registration status and capabilities of media resources on a gateway.

Answer

show dial-peer voice

Answer

show media resources

Answer

show voice gateway status

Question 7

You are implementing a QoS policy on a WAN edge router. You have a requirement to prioritize video traffic. Which queueing mechanism is recommended by Cisco to minimize jitter and latency for video streams?

Accepted Answer

Low Latency Queuing (LLQ). Low Latency Queuing (LLQ) combines priority queuing with Class-Based Weighted Fair Queuing (CBWFQ) to provide strict priority for latency-sensitive traffic like video.

Answer

Weighted Fair Queuing (WFQ)

Answer

Priority Queuing (PQ) only

Answer

Random Early Detection (RED)

Question 8

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.. MTPs are used to provide features like DTMF interworking (e.g., SIP to H.323) when the endpoints do not support the same method.

Answer

To limit the bandwidth consumed by a call.

Answer

To provide codec transcoding services.

Answer

To cache video streams for faster playback.

Question 9

A network administrator is troubleshooting one-way audio issues between a Cisco IP Phone and a Cisco TelePresence endpoint. The path traverses a router with a configured class-map. Which command would you use to verify the packet markings on the ingress interface?

Accepted Answer

show policy-map interface. The 'show policy-map interface' command is the primary tool to verify QoS statistics and confirm if packets are being classified and marked as expected.

Answer

show class-map configuration

Answer

show ip rtp statistics

Answer

show qos interface

Question 10

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.. The Transcoder must be registered to a Media Resource Group (MRG) that is included in the MRGL assigned to the device pool or the device itself.

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 11

What is the default behavior for DSCP markings on traffic originating from a Cisco IP Phone that has not been configured with specific QoS policies?

Accepted Answer

Marked as DSCP 46 for voice and CS3 for signaling. By default, Cisco IP Phones mark voice media as DSCP 46 (EF) and signaling as DSCP 24 (CS3) automatically.

Answer

Marked as DSCP 34 (AF41)

Answer

Traffic is not marked until a policy-map is applied

Answer

Marked as DSCP 0 (Best Effort)

Question 12

You are configuring QoS for a Cisco Unified Communications Manager (CUCM) deployment. You need to ensure that audio media traffic between endpoints is marked correctly. Which DSCP value should be assigned to RTP audio traffic according to the Cisco SRND best practices?

Accepted Answer

DSCP 46 (EF). Cisco best practices recommend marking RTP audio traffic with EF (Expedited Forwarding) or DSCP 46 to ensure low latency and low jitter.

Answer

DSCP 34 (AF41)

Answer

DSCP 24 (CS3)

Answer

DSCP 0 (BE)

Question 13

Which DSCP value is recommended for Call Signaling traffic in a Cisco Unified Communications network?

Accepted Answer

CS3 (24). CS3 (DSCP 24) is the recommended value for signaling traffic to prioritize it over standard data traffic.

Answer

AF31 (26)

Answer

EF (46)

Answer

AF41 (34)

Question 14

When using 'RSVP' for Call Admission Control (CAC), what happens if the available bandwidth on the path is less than the requested amount?

Accepted Answer

The call is blocked. RSVP is a resource reservation protocol. If the path cannot support the required bandwidth, the call is rejected by the system.

Answer

The call is placed but with a lower quality codec

Answer

The call is put on hold until bandwidth is available

Answer

The call proceeds, but marks the packets with Best Effort

Question 15

An administrator needs to enforce a bandwidth limit for video calls at a specific site in CUCM. Which configuration object should be used?

Accepted Answer

Location. Locations in CUCM are used to define available bandwidth for audio and video calls at a specific geographic site.

Answer

Region

Answer

Partition

Answer

Device Pool

Question 16

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. If video traffic is not being classified into the correct class-map, it falls into the default class, which is likely experiencing congestion and drops.

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 17

In a multi-site deployment, you have a requirement to transcode between G.711 and G.729. If the transcoder resources are exhausted, what is the expected outcome for a new call requiring this conversion?

Accepted Answer

The call will be rejected. If the MRGL is exhausted or no transcoder is available, the call will fail the capability negotiation and be rejected by CUCM.

Answer

The call will use G.711 regardless

Answer

The call will proceed with no audio

Answer

The call will fall back to an MTP

Question 18

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 'bandwidth' command allows you to reserve a specific amount of bandwidth for a class within a policy-map.

Answer

rate-limit [kbps]

Answer

guarantee [kbps]

Answer

priority bandwidth

Question 19

You are configuring a Cisco IOS router to perform traffic shaping for voice traffic. Why is traffic shaping often used in conjunction with queuing?

Accepted Answer

To prevent interface congestion by smoothing out traffic bursts. Traffic shaping smooths out bursts of traffic, preventing the buffer overflows that would lead to packet loss and poor voice quality.

Answer

To prioritize voice over data traffic

Answer

To reduce the CPU utilization of the router

Answer

To increase the total throughput of the interface

Question 20

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

Accepted Answer

Locations CAC. Location-based Call Admission Control (CAC) is the native feature in CUCM that restricts calls when bandwidth limits are reached.

Answer

Gatekeeper

Answer

Bandwidth Manager

Answer

RSVP