CLCOR Hard Questions — 25 Difficult Questions

Question 1

A user is unable to receive incoming PSTN calls via a Webex Calling Local Gateway. You observe that the INVITE from the provider reaches the CUBE, but the CUBE sends a 403 Forbidden. What is the most likely cause?

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

Accepted Answer

The incoming dial peer is missing or misconfigured. A 403 Forbidden response from the CUBE indicates that the incoming INVITE is being rejected due to a dial peer mismatch. The incoming dial peer is responsible for matching incoming calls and applying the correct configuration; if it is missing or misconfigured, the CUBE cannot route the call and returns 403.

Answer

The PSTN provider is using an unsupported codec

Answer

The Webex cloud is unreachable

Answer

The user's directory number is not in the PSTN white list

Question 2

When using 'Call Pickup', how does a user pick up a call that is ringing on another phone in the same pickup group?

Accepted Answer

By pressing the 'Pickup' softkey.. Call Pickup allows a user to answer a call ringing on another phone in the same pickup group by pressing the 'Pickup' softkey (or dialing the pickup group code). The softkey triggers the Call Pickup feature, which redirects the ringing call to the user's phone. This is a standard CUCM feature for group call answering.

Answer

By dialing the target phone extension.

Answer

By selecting 'Hold' on their own line.

Answer

By accessing the CUCM web interface.

Question 3

A CUBE is configured to connect to a SIP provider that uses a non-standard SIP port (not 5060) for signaling. The CUBE must send outbound INVITEs to this provider on port 5080. Which configuration is required on the outbound dial-peer to achieve this?

Accepted Answer

session target ipv4:192.0.2.1:5080. For a SIP dial-peer, the destination IP address and port are configured using the 'session target ipv4::' command. This directs outbound SIP signaling to the specified IP and port. In this scenario, the provider uses port 5080, so the session target must include that port. Other commands like destination-pattern or outbound-proxy serve different purposes and would not correctly direct the INVITE to the non-standard port.

Answer

voice-class sip url sip:192.0.2.1:5080

Answer

destination-pattern 5080

Answer

voice-class sip outbound-proxy ipv4:192.0.2.1:5080

Question 4

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 5

You are deploying Webex Hybrid Data Security (HDS). After deploying the virtual machines for the HDS nodes, you find they are not appearing in Control Hub. What is the first step you should take to troubleshoot the registration?

Accepted Answer

Check the local log files in the HDS node using the CLI.. When HDS nodes do not appear in Control Hub, the first troubleshooting step is to check the local log files on the HDS node via the CLI. The logs will show whether the node successfully reached the Webex cloud, whether the registration token was accepted, and whether there are certificate or connectivity errors. This is the fastest way to identify the root cause before making configuration changes.

Answer

Disable the firewall on the HDS node.

Answer

Restart the Cisco Webex Hybrid Services host.

Answer

Re-download the management certificate.

Question 6

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 7

You want to ensure that a specific device pool always uses a G.729 codec for inter-site calls. What is the most effective approach?

Accepted Answer

Define a Region matrix setting the audio bitrate between the two regions to G.729.. Codec selection for inter-site calls in CUCM is governed by Regions and their associated Region matrix, which defines the maximum audio codec (bitrate) allowed between any two regions. To force G.729 between two sites, you assign each site's devices to a region and set the matrix entry between those regions to G.729. This is the only supported mechanism that enforces codec choice based on the relationship between calling and called parties' locations.

Answer

Use a translation pattern.

Answer

Set the codec in the device pool.

Answer

Configure the codec on the SIP trunk.

Question 8

Which THREE items are included in a standard SIP REGISTER request?

Accepted Answer

To Header. The To header (B) is mandatory in a SIP REGISTER request because it carries the address-of-record (AOR) whose bindings are being registered, e.g. To: <sip:alice@example.com>. The From header (D) is also required and identifies the registrant submitting the request, typically matching the AOR and containing a tag parameter for dialog identification. The Contact header (E) is essential because it supplies the binding information — the SIP URI (and optional q value and expires parameter) where the user agent can be reached, which is the core purpose of REGISTER. Alert-Info (A) is not part of a standard REGISTER; it is used in INVITE responses to specify ringback tones. A body with SDP (C) is not included in a standard REGISTER since REGISTER does not negotiate media sessions; SDP is carried in INVITE and its responses.

Answer

Alert-Info

Answer

Body (SDP)

Question 9

When troubleshooting CUBE SIP normalization, which tool allows you to view the normalized SIP messages in real-time?

Accepted Answer

debug ccsip messages. The command `debug ccsip messages` (B) enables real-time debugging of SIP messages on Cisco Unified Border Element (CUBE). It displays the actual SIP messages sent and received, including the normalized messages after SIP normalization profiles are applied, allowing you to verify the normalization logic.

Answer

show voice class sip-profiles

Answer

debug voip ccapi inout

Answer

debug sip-ua

Answer

show sip-profile

Question 10

Which THREE actions are possible using SIP profiles on a CUBE?

Accepted Answer

Modify SIP headers. SIP profiles on Cisco Unified Border Element (CUBE) are used to manipulate SIP signaling by inspecting and altering SIP messages, so option A (Modify SIP headers) is correct because rules within a SIP profile can rewrite existing header values such as From, To, or Diversion. Option B (Add SIP headers) is correct because SIP profiles support the 'request' and 'response' header-insertion rules that inject new headers into inbound or outbound SIP messages. Option C (Remove SIP headers) is correct because SIP profiles can strip unwanted headers via header-removal rules, which is common for privacy or interop scenarios. Option D (Change voice codec) is not a SIP-profile function; codec negotiation is handled by dial peers (codec preference lists, 'codec' commands) and SDP, not by SIP header manipulation. Option E (Route calls to PSTN) is also not a SIP-profile action; call routing is determined by dial-peer matching and translation rules, while SIP profiles only affect SIP message content.

Answer

Change voice codec

Answer

Route calls to PSTN

Question 11

You are configuring Webex Hybrid Data Security (HDS). What is the purpose of the 'Key Management Service' (KMS) in this architecture?

Accepted Answer

To allow the enterprise to maintain control over encryption keys. In Webex Hybrid Data Security (HDS), the Key Management Service (KMS) is a customer-deployed component that stores and manages the encryption keys used to encrypt Webex content (messages, files, whiteboards). Its core purpose is to give the enterprise sole control over those keys, so Cisco cannot decrypt the content — this is the 'hybrid' data security promise. Thus, the correct answer is that KMS allows the enterprise to maintain control over encryption keys.

Answer

To authenticate users against local Active Directory

Answer

To facilitate the storage of encrypted meeting recordings

Answer

To manage SIP signaling encryption

Question 12

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. In Cisco Unified CM, the Location object is the configuration element that enforces call admission control (CAC) by defining the maximum audio and video bandwidth available between locations. When a video call is placed, CUCM subtracts the call's bandwidth from the Location's video bandwidth pool, and if the limit is exceeded, the call is denied or rerouted. This makes Location the correct object for enforcing a per-site bandwidth limit for video calls.

Answer

Region

Answer

Partition

Answer

Device Pool

Question 13

You are implementing Webex Calling with a Local Gateway. The requirement is to maintain internal dial plan transparency for existing extension-to-extension dialing. What must you configure?

Accepted Answer

Location-based routing and dial plan normalization. Location-based routing and dial plan normalization are essential for maintaining internal dial plan transparency. Location-based routing ensures that calls are routed according to the user's location, and dial plan normalization translates dialed digits into a format that the local gateway can process, preserving extension-to-extension dialing.

Answer

Global Dial Plan Replication

Answer

Directory sync override

Answer

PSTN overflow routing

Question 14

An administrator is troubleshooting a failed Hybrid Calendar setup. The 'Connector' shows as 'Down' in Control Hub. What is the most likely reason?

Accepted Answer

The Expressway-C host cannot reach the cloud over port 443.. The Hybrid Calendar Connector in Control Hub relies on the on-premises Expressway-C (or Cisco Webex Hybrid Services connector) maintaining an outbound TLS connection to Webex cloud endpoints over TCP 443. When that outbound path is blocked by a firewall, proxy, or DNS failure, Control Hub reports the connector status as 'Down' because the heartbeat to the cloud cannot be established. License, user password, and AD group issues would not cause the connector itself to show Down — they would affect calendar processing for individual users, not the connector health state.

Answer

The calendar integration license is invalid.

Answer

The user's password expired.

Answer

The user is not in the correct group in Active Directory.

Question 15

A CUBE is receiving calls but rejecting them due to '488 Not Acceptable Here'. What is the most likely reason?

Accepted Answer

Codec mismatch. SIP 488 'Not Acceptable Here' is returned when the called party cannot support the media parameters in the offer — most commonly a codec mismatch where the offered codec (e.g., G.729) is not configured on any matching dial-peer on the CUBE. CUBE rejects the INVITE because it cannot negotiate a compatible codec between the inbound and outbound legs.

Answer

Authentication failure

Answer

SIP registration expired

Answer

Dial-peer inactive

Question 16

You are troubleshooting a Webex Hybrid Calendar issue where meetings are missing for a specific user. What tool can you use to check the 'Calendar API' calls?

Accepted Answer

Expressway-C Calendar Connector status page.. The Expressway-C Calendar Connector status page is the correct tool because in Webex Hybrid Calendar (Exchange/Office 365 integration), the Expressway-C hosts the Calendar Connector service that makes Calendar API calls to the on-premises or cloud calendar. Its status page shows connector health, API call results, and per-user sync diagnostics, making it the right place to trace missing meetings for a specific user.

Answer

The Cisco Webex App debug logs.

Answer

Control Hub Troubleshooting tool.

Answer

Active Directory event viewer.

Question 17

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 18

You are configuring Webex Hybrid Calendar with Microsoft 365. You want to ensure that 'Join' buttons appear on video devices for meetings. What must be configured?

Accepted Answer

Webex Room devices must be registered to the same organization.. For Webex Hybrid Calendar with Microsoft 365 to show 'Join' buttons on video devices, the Webex Room devices must be registered to the same Webex organization as the users whose calendars are being processed. The Join button is injected into the meeting invite by the Hybrid Calendar service, and the device must be able to resolve the meeting to a Webex meeting in that organization. If the device is registered to a different org, the calendar connector cannot associate the meeting with the device, and no Join button appears.

Answer

The Expressway-C must be in the DMZ.

Answer

Microsoft 365 AutoDiscover must be enabled.

Answer

The user must have a Webex Calling license.

Question 19

You need to support Opus codec on a Cisco IP Phone 8865. Which configuration object must be updated to allow this codec?

Accepted Answer

Audio Codec Preference List. Opus is a codec, and in Cisco Unified Communications Manager codec support is governed by the Audio Codec Preference List, which defines which codecs a device offers and in what priority. To allow Opus on an 8865, you must add Opus to the codec preference list assigned to the device or device pool. The SIP Profile, Common Phone Profile, and Device Defaults do not control codec availability.

Answer

SIP Profile

Answer

Common Phone Profile

Answer

Device Defaults

Question 20

Which THREE steps are involved in the 'Cisco Unified Communications Manager' disaster recovery process?

Accepted Answer

Perform a full system backup using DRS.. Option B is correct because the Cisco Unified Communications Manager disaster recovery process begins with a full system backup using the Disaster Recovery System (DRS), which captures the database, configuration, and other critical components needed for later restoration. Option D is correct because after the backup, the data must be restored using the DRS Restore tool, which repopulates the newly installed CUCM instance with the saved configuration and database. Option E is correct because disaster recovery requires installing a fresh CUCM instance on the new hardware before the DRS restore can be performed, since the restore targets a clean, matching CUCM installation. Option A is incorrect because deleting existing TFTP files is not a defined step in the CUCM disaster recovery process and could disrupt phone registration and configuration file delivery. Option C is incorrect because 'utils dbreplication reset' is used to rebuild database replication between cluster nodes, not as a standard step in the disaster recovery backup and restore workflow.

Answer

Delete the existing TFTP files.

Answer

Run the 'utils dbreplication reset' command.