27 questions · Protocols And Endpoints · All types, answers revealed
You have a requirement to use secure signaling for SIP endpoints. Which protocol and port combination must be used in the SIP Security Profile?
TLS on 5061 provides secure signaling.
Why this answer
SIPS (SIP over TLS) uses port 5061 to ensure encrypted signaling.
A Webex Desk Pro is failing to provision via the Cisco Webex Control Hub. The device displays 'Provisioning Error'. Which configuration component is primarily responsible for holding the authentication credentials required for the device to pull its configuration?
The activation code is the primary method for secure onboarding.
Why this answer
The Activation Code or the specific Device Configuration profile in Control Hub provides the credentials needed for the device to authenticate against the cloud service.
You are troubleshooting intermittent audio quality. You notice that RTCP packets are arriving with high variance. What does this indicate?
High variance in arrival time is the definition of jitter.
Why this answer
Intermittent audio quality and high variance in RTCP reports point directly to network jitter.
To ensure that G.729 is used for all inter-site calls but G.711 is used for intra-site calls, what specific CUCM construct must you define?
Region relationships explicitly define codec limits between sites.
Why this answer
You must define Regions and then assign the 'Region Relationship' to dictate the codec allowed between those regions.
When a SIP phone initiates a call, which message does the CUCM send to acknowledge the initial INVITE?
100 Trying is the provisional response.
Why this answer
A '100 Trying' message is the standard response to indicate that the INVITE has been received and is being processed.
You need to support Opus codec on a Cisco IP Phone 8865. Which configuration object must be updated to allow this codec?
This list defines which codecs the endpoint is allowed to negotiate.
Why this answer
The 'Common Phone Profile' or 'SIP Profile' doesn't contain codec lists; the 'Audio Codec Preference List' must be modified and applied to the device or the region/location configuration.
You are troubleshooting a scenario where G.711 is being used instead of the expected Opus codec between two endpoints in the same region. What is the most likely cause in the CUCM configuration?
The codec preference list dictates the order and availability of codecs.
Why this answer
If the 'Audio Codec Preference List' or the 'Region' setting does not include Opus as a supported codec, CUCM will fall back to G.711.
You are troubleshooting a registration issue where the phone sends a REGISTER request, but the server does not respond. What is the most likely issue?
Lack of response indicates a path failure.
Why this answer
If the phone sends a request and gets no response, it is a reachability or network path issue (firewall/ACL).
Which TWO features are provided by the Cisco Webex App when registered as a Softphone?
Required for call control.
Why this answer
Webex provides softphone signaling (SIP) and audio/video media capabilities.
Which field in the SIP INVITE SDP body specifies the media attributes such as codec type?
'm=' defines the media stream and codec attributes.
Why this answer
The 'm=' (media) line specifies the media type, port, protocol, and codec information.
An endpoint sends a SIP REGISTER request. CUCM returns a 401 Unauthorized response. What is the next logical step in the SIP signaling flow for the endpoint?
The endpoint must respond to the challenge with credentials.
Why this answer
The 401 response challenges the endpoint to provide credentials (Digest authentication). The endpoint must resend the REGISTER request with the Authorization header.
A Cisco IP Phone 8841 is failing to register to Cisco Unified Communications Manager. You check the phone settings and see the TFTP server address is correct. Which protocol and port should you monitor on the gateway or firewall to verify the initial registration attempt?
SIP registration occurs over 5060 by default.
Why this answer
SIP registration uses UDP or TCP port 5060 for non-secure, or TLS port 5061 for secure registration.
Which TWO tasks must be performed when moving a phone from one CUCM cluster to another?
Reset forces the phone to re-download the config from the new server.
Why this answer
You must change the TFTP server address and potentially reset the device to clear the old registration data.
Which THREE items are included in a standard SIP REGISTER request?
Target user/address.
Why this answer
The 'To', 'From', and 'Contact' headers are mandatory in a SIP REGISTER request.
When configuring an IP phone for automatic provisioning, which DHCP option is most commonly used to provide the TFTP server address to the phone?
Option 150 is the industry standard for Cisco voice devices.
Why this answer
DHCP Option 150 is the standard method for Cisco IP Phones to discover the TFTP server address.
An IP phone is stuck in a boot loop. You suspect a corrupted firmware image. Which process would you initiate to force the phone to download a new image?
Factory reset clears local settings and forces a re-download of firmware.
Why this answer
Performing a 'Factory Reset' or updating the 'Load Information' in the Device configuration in CUCM will trigger a forced update.
Which protocol is primarily used for the transmission of real-time voice and video data between two endpoints?
RTP carries the actual media stream.
Why this answer
RTP (Real-time Transport Protocol) is the standard for media transport.
Which TWO protocols are used for managing the quality and monitoring of VoIP sessions?
RTCP is the feedback protocol for RTP.
Why this answer
RTCP is used for quality feedback, and SNMP or various management protocols are used for monitoring.
Which protocol provides the signaling for Webex Room devices when they are registered to CUCM (on-premises)?
SIP is the standard protocol for Cisco endpoints.
Why this answer
Webex Room devices can use SIP to register to on-premises CUCM systems.
Which THREE methods are used by Cisco IP phones to obtain their configuration files?
Used in newer firmware/webex environments.
Why this answer
DHCP options, manual entry, and auto-discovery/TFTP are standard methods.
An endpoint using the Opus codec is experiencing one-way audio. The SDP exchange indicates that the endpoint is offering a wideband range. Where in CUCM would you modify the Region settings to force the use of a specific codec for this endpoint?
Regions define the max audio bit rate used between endpoints.
Why this answer
The Region settings in CUCM define the maximum audio bit rate between regions; the codec is chosen based on these region constraints.
Which THREE codecs are natively supported by the Cisco IP Phone 8800 series?
Modern wideband codec.
Why this answer
G.711, G.729, and Opus/G.722 are widely supported across the 8800 series.
Which component in the Cisco Collaboration architecture provides the initial configuration files (XML) to an IP phone upon registration?
The TFTP service delivers the configuration files.
Why this answer
The TFTP service in CUCM acts as the repository for device configuration files.
You are monitoring RTP traffic using a protocol analyzer. You observe that the Payload Type field in the RTP header is set to 0. Which codec is currently in use?
Payload type 0 is reserved for G.711 u-law.
Why this answer
In G.711 PCMU (u-law), the assigned payload type is 0 according to RFC 3551.
Which THREE network conditions contribute to poor VoIP call quality in an RTP stream?
Delay causes conversation overlaps.
Why this answer
Latency, jitter, and packet loss are the primary enemies of voice quality.
You need to verify that an endpoint is correctly sending RTCP reports to Cisco Unified Communications Manager. Which field in the RTCP packet header would you examine to track the jitter statistics?
The interarrival jitter field explicitly reports network quality.
Why this answer
RTCP SR (Sender Report) and RR (Receiver Report) packets contain interarrival jitter fields to help calculate network quality.
Which TWO factors significantly impact the choice of audio codec during a call setup in CUCM?
Orders the available codecs.
Why this answer
Bandwidth availability (Regions) and codec preference (Codec List) are the main determinants.
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