CLCOR Infrastructure And Design — 20 Questions

Question 1

You are performing a network readiness assessment for a Cisco Webex Room Kit deployment. The current network uses a legacy infrastructure with a MTU of 1500 bytes. What is the recommended practice for handling potential fragmentation issues for video traffic streams?

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

Accepted Answer

Implement Jumbo Frames (MTU 9000) across the entire media path.. Video traffic is sensitive to jitter and delay. Ensuring that the network supports a larger MTU or preventing fragmentation by sizing packets correctly is critical.

Answer

Force fragmentation by enabling ICMP unreachable messages.

Answer

Reduce the video resolution to 360p to keep packet sizes small.

Answer

Disable QoS to allow larger packets to traverse the path.

Question 2

You are designing a high availability solution for Cisco Unity Connection. Which service must be running and correctly configured on both the primary and secondary servers to facilitate automatic failover?

Accepted Answer

Connection High Availability. Cisco Unity Connection uses the Connection High Availability service to synchronize data and heartbeat between the cluster nodes.

Answer

Cisco Tomcat Service

Answer

Cisco Database Layer Monitor

Answer

Cisco Unity Connection Message Transfer Agent

Question 3

You are designing a Cisco Unified Communications Manager (CUCM) cluster with geographically dispersed nodes. To ensure optimal voice quality and call signaling efficiency, which mechanism should you configure to prevent the transmission of unnecessary SIP signaling traffic over high-latency WAN links?

Accepted Answer

Configure SIP Trunk SIP Profile timers to increase INVITE timeout values.. SIP proxy timers and keepalive settings are critical for WAN links, but configuring SIP Trunk SIP Profile timers allows for better management of transaction timeouts across high-latency links.

Answer

Disable SIP OPTIONS keepalives on all trunk configurations.

Answer

Set the DSCP value to EF for all SIP signaling traffic.

Answer

Enable SIP REFER method support on all inter-cluster trunks.

Question 4

You are deploying a CUBE (Cisco Unified Border Element) for SIP trunking. Which feature allows CUBE to hide the internal network topology from the service provider?

Accepted Answer

SIP Header Normalization. SIP Header Manipulation/Normalization is used to rewrite headers and remove sensitive internal network information like private IP addresses.

Answer

Media Proxy

Answer

Call Admission Control (CAC)

Answer

Registration Proxy

Question 5

Which TWO of the following QoS mechanisms are recommended for voice traffic to minimize delay?

Accepted Answer

Low Latency Queuing (LLQ). LLQ (Low Latency Queuing) and Priority Queuing are the two standard methods to ensure voice traffic gets the necessary priority to minimize latency.

Answer

Random Early Detection (RED)

Answer

Weighted Fair Queuing (WFQ)

Answer

Traffic Shaping

Question 6

When deploying a high-availability CUCM cluster, how many subscribers are recommended to be associated with a single publisher for optimal database performance?

Accepted Answer

8. Cisco design guides recommend keeping the cluster size within specific limits to ensure database replication efficiency, typically a maximum of 8 subscribers per publisher.

Answer

16

Answer

4

Answer

32

Question 7

A network engineer is deploying Cisco Unified Border Element (CUBE) and must ensure that voice traffic is prioritized correctly across the enterprise network. Which command correctly maps the voice traffic DSCP value to the correct priority queue in a Cisco IOS-XE router?

Accepted Answer

class-map match-any VOICE; match dscp ef; policy-map VOICE-POLICY; class VOICE; priority 1000. The 'priority' command within a policy-map defines the LLQ (Low Latency Queuing) behavior for voice traffic.

Answer

class-map match-any VOICE; match protocol sip; policy-map VOICE-POLICY; class VOICE; queue-limit 100

Answer

class-map match-all VOICE; match dscp cs4; policy-map VOICE-POLICY; class VOICE; bandwidth 1000

Answer

class-map match-any VOICE; match dscp ef; policy-map VOICE-POLICY; class VOICE; fair-queue

Question 8

In a Cisco collaboration design, you are tasked with identifying the DHCP Option required for Cisco IP Phones to discover the TFTP server address automatically. Which option is standard for this purpose?

Accepted Answer

Option 150. DHCP Option 150 is the standard Cisco-specific option used to provide the IP addresses of the TFTP servers to IP endpoints.

Answer

Option 66

Answer

Option 128

Answer

Option 43

Question 9

When designing an NTP deployment for a Cisco Collaboration environment, what is the best practice for time synchronization across CUCM nodes?

Accepted Answer

Point all CUCM nodes to the same external NTP stratum 1 or 2 servers.. CUCM nodes must point to the same reliable external Stratum 1 or 2 NTP servers to ensure call logs and security certificates remain synchronized.

Answer

Configure NTP only on the publisher node.

Answer

Point each CUCM node to a different NTP server for redundancy.

Answer

Use the publisher as the NTP server for all subscriber nodes.

Question 10

Which design principle must be followed when implementing a centralized call processing deployment with remote branch offices connected via a WAN?

Accepted Answer

Enable SRST on the local branch gateway to handle call processing during a WAN outage.. When the WAN link fails, Survivable Remote Site Telephony (SRST) or Cisco Unified SRST is required to keep the phones registered and functional.

Answer

Deploy a dedicated CUCM node in every branch office.

Answer

Configure H.323 gateways at each site to communicate directly with all remote phones.

Answer

Use RSVP to guarantee bandwidth across the WAN for signaling.

Question 11

You are configuring DNS SRV records to support Jabber service discovery. Which domain format is correct for the _collab-edge._tls record?

Accepted Answer

_collab-edge._tls.example.com. The _collab-edge._tls record is used by Cisco Expressway-E for MRA discovery, and it must point to the FQDN of the Expressway-E cluster.

Answer

_tls._collab-edge.example.com

Answer

collab-edge.example.com._tls

Answer

_collab-edge._tcp.example.com

Question 12

Which network condition is the most significant contributor to poor voice quality in a VoIP environment?

Accepted Answer

Jitter. Jitter, packet loss, and latency are the three main contributors to poor voice quality, but jitter (variation in packet arrival) is often the most difficult to resolve once it reaches the end device.

Answer

Low CPU usage on the router

Answer

Static IP addresses

Answer

High bandwidth usage

Question 13

You are verifying the network readiness for a Cisco TelePresence endpoint. Which tool would you use to measure the packet loss, latency, and jitter on the path to the CUCM cluster?

Accepted Answer

IP SLA. IP SLA (Service Level Agreement) is the Cisco IOS feature used to generate synthetic traffic to measure network performance metrics.

Answer

NetFlow

Answer

SNMP

Answer

SPAN

Question 14

You are designing a solution for secure voice signaling. Which protocol provides encryption for SIP signaling messages in a CUCM environment?

Accepted Answer

TLS. SIP messages are encrypted using TLS (Transport Layer Security), which is referred to as SIPS in the context of secured signaling.

Answer

IPsec

Answer

SRTP

Answer

SSH

Question 15

A collaboration designer must ensure that inter-cluster calls between two CUCM clusters remain secure. Which mechanism must be implemented to ensure media remains encrypted from end to end?

Accepted Answer

Ensure SRTP is enabled on the SIP Trunk Security Profile.. SRTP must be used across the SIP inter-cluster trunk to ensure the media stream is encrypted between endpoints in different clusters.

Answer

Disable SIP inspection on the firewalls.

Answer

Configure a VPN between the two clusters.

Answer

Enable MTP (Media Termination Point) for all calls.

Question 16

You are deploying a Cisco Expressway-E in a DMZ. Which port must be opened on the external firewall to allow for H.460.18/19 firewall traversal for H.323 endpoints?

Accepted Answer

1720. Port 1720 is the standard H.323 signaling port used for traversal through the Expressway-E.

Answer

5061

Answer

8080

Answer

443

Question 17

In a multisite WAN deployment, which codec should you choose to balance voice quality and bandwidth consumption across a constrained link?

Accepted Answer

G.729. G.729 is the standard low-bandwidth codec that provides acceptable voice quality at 8kbps.

Answer

G.711

Answer

AAC-LD

Answer

G.722

Question 18

When designing for high availability of Cisco Unified Communications Manager (CUCM) services, which specific configuration ensures that a secondary node takes over call processing if the primary node fails?

Accepted Answer

Configure a CUCM Group in the Device Pool with multiple servers.. The Device Pool and the associated Cisco Unified Communications Manager Group define which servers a device registers with and in what order.

Answer

Set the 'Call Processing Load' value in the System settings.

Answer

Enable Auto-registration for all phones.

Answer

Configure the cluster-wide failover parameter in the Service Parameter page.

Question 19

You have a CUCM cluster with high utilization. Which parameter, when adjusted, helps mitigate the load on the TFTP service during a large-scale phone deployment?

Accepted Answer

TFTP File Load Factor. Setting the 'Enable Caching of Signed Files' and 'TFTP File Load Factor' helps optimize the TFTP server's ability to serve requests without overloading.

Answer

Keepalive Interval

Answer

Max Phone Registrations

Answer

Registration Timeout

Question 20

Which component in a Cisco Collaboration design is responsible for providing the dial tone and call routing logic for IP phones?

Accepted Answer

Cisco Unified Communications Manager. CUCM (Cisco Unified Communications Manager) is the primary call control agent responsible for call processing, routing, and device management.

Answer

Cisco Expressway

Answer

Cisco Unity Connection

Answer

Cisco CUBE