Free Cisco 300-820 CLHCT practice questions

10 free Cisco 300-820 CLHCT practice questions with the correct answer and a full explanation for each, taken from the CertStash pack of 277 questions. Work through them, then open each answer to check your reasoning.

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Question 1

Which complication does a NAT introduce in SDP for a SIP call?

  1. Additional headers due to NAT encapsulation can cause the packet size to exceed the MTU.
  2. When the client is behind a NAT they may be unable to determine the appropriate offset due to time zones.
  3. The IP address specified in the connection data field may be an unrouteable internal address.
  4. The encryption keys advertised in the SDP are only valid for clients not behind a NAT.
Show answer and explanation

Correct answer: C. The IP address specified in the connection data field may be an unrouteable internal address.

may be an unrouteable internal address. When a SIP client is behind NAT, the SDP connection data field (c-line) contains the private internal IP address of the client, which is not routable on the public Internet. Remote endpoints cannot reach this address to establish media streams, requiring NAT traversal solutions to rewrite these addresses with the public NAT gateway address.

Why the other options are wrong

  • A. NAT encapsulation does not add headers that would exceed MTU; the issue is address translation, not packet size.
  • B. Time zones are irrelevant to NAT complications in SDP; this conflates unrelated concepts.
  • D. Encryption keys in SDP are not invalidated by NAT; the issue is address reachability, not key validity.

Question 2

A company already has a Cisco Unified Communications Manager for internal audio and video traffic, but it requires video communication with external partners and customers. It is important to ensure security for the deployment and the connectivity.

What must be set up to enable this requirement?

  1. Cisco Unified Border Element and Cisco ASA Firewall
  2. Cisco Unified Border Element and Cisco Firepower Firewall
  3. Cisco Expressway-C and Cisco Expressway-E
  4. Cisco Expressway-C and Cisco Unified Border Element
Show answer and explanation

Correct answer: C. Cisco Expressway-C and Cisco Expressway-E

Cisco Expressway-C and Expressway-E provide secure external communication for Unified Communications. Expressway-C resides on the internal network and integrates with Unified Communications Manager, while Expressway-E sits at the network edge to handle external traffic. This architecture enables secure video communication with external partners while maintaining internal UCM registration.

Why the other options are wrong

  • A. ASA Firewall is a perimeter firewall but does not provide the protocol interworking and traversal functions needed for unified communications.
  • B. Firepower Firewall is a next-generation firewall but cannot replace Expressway's unified communications-specific capabilities.
  • D. Unified Border Element provides interworking but is not the correct pairing with Expressway-C for this secure external communication scenario.

Question 3

When an Expressway-E is configured for static NAT, which Session Description Protocol attribute is modified to reflect the NAT address?

  1. SDP b-line
  2. SIP record route
  3. SDP c-line
  4. SDP m-line
Show answer and explanation

Correct answer: C. SDP c-line

The SDP c-line (connection data field) specifies the IP address and address type for media connections. When Expressway-E is configured for static NAT, it modifies the c-line to advertise the external NAT address instead of the internal address, allowing external endpoints to correctly route media packets to the translated address.

Why the other options are wrong

  • A. The SDP b-line specifies bandwidth information, not addresses.
  • B. SIP record route is a SIP header mechanism, not an SDP attribute.
  • D. The SDP m-line specifies media type and port information, not the connection address.

Question 4

A company is installing Cisco Collaboration infrastructure and one of the requirements is that they must be able to communicate with many external parties that are using H.323 and SIP. Internally they want to register the endpoints only on SIP.

Which functionality would describe the feature that needs to be enabled and where to achieve this?

  1. Interworking in Expressway-C
  2. Transcoding in Cisco Unified Communications Manager
  3. Transcoding in Expressway-C
  4. Interworking in Cisco Unified Communications Manager
Show answer and explanation

Correct answer: A. Interworking in Expressway-C

Interworking functionality converts between different signaling protocols, allowing SIP endpoints internally to communicate with external H.323 endpoints. This capability is configured on Expressway-C, which acts as the internal proxy and can perform protocol conversion between SIP and H.323 at the boundaries.

Why the other options are wrong

  • B. Transcoding converts between different media codecs, not signaling protocols.
  • C. Transcoding is for media conversion; Expressway-C handles interworking but transcoding is not the correct feature for protocol conversion.
  • D. Unified Communications Manager does not provide interworking between H.323 and SIP; this is an Expressway function.

Question 5

What is a key configuration requirement for Hybrid Message Service High Availability deployment with multiple IM and Presence clusters?

  1. You must have the Intercluster Sync Agent working across your IM and Presence clusters.
  2. You must have the Intercluster Lookup Service working across all of your IM and Presence clusters.
  3. Your IM and Presence Service clusters must have Multiple Device Messaging disabled.
  4. AXL service should be activated only on the publisher of each IM and Presence cluster.
Show answer and explanation

Correct answer: A. You must have the Intercluster Sync Agent working across your IM and Presence clusters.

across your IM and Presence clusters. The Intercluster Sync Agent is a key component for Hybrid Message Service High Availability deployments. It synchronizes data across multiple IM and Presence clusters, ensuring that user presence, messaging state, and other critical information remain consistent across the clustered environment.

Why the other options are wrong

  • B. The Lookup Service provides service discovery but is not the specific component for high availability data synchronization across clusters.
  • C. Multiple Device Messaging is a client feature independent of HA cluster requirements.
  • D. AXL service can be activated on multiple nodes and is not limited to only the publisher in HA deployments.

Question 6

Cisco Collaboration endpoints are exchanging encrypted signaling messages.

What is one major complication in implementing NAT ALG for voice and video devices?

  1. Internal endpoints cannot use addresses from the private address space.
  2. The NAT ALG cannot inspect the contents of encrypted signaling messages.
  3. NAT ALG introduces jitter in the voice path.
  4. Source addresses cannot provide the destination addresses that remote endpoints should use for return packets.
Show answer and explanation

Correct answer: B. The NAT ALG cannot inspect the contents of encrypted signaling messages.

encrypted signaling messages. NAT Application Level Gateway (ALG) functionality requires inspection of signaling message contents to identify and translate embedded IP addresses and port numbers. When signaling is encrypted, the NAT ALG cannot inspect the encrypted payload, making it unable to perform address translation for embedded media addresses, breaking media connectivity.

Why the other options are wrong

  • A. Private address spaces are routinely used behind NAT; this is not a complication of NAT ALG.
  • C. NAT ALG operates at the application layer and does not introduce jitter in media paths.
  • D. Source addresses inherently provide the information needed for return packets; this is not a NAT ALG complication.

Question 7

What are two reasons why port 8443 is unreachable from the Internet to the Expressway-E? (Choose two.)

  1. The MRA license is missing on the Expressway-E.
  2. The Unified Communications zone is down.
  3. Transform is not configured on Expressway-E.
  4. The SRV record for _cisco-uds is misconfigured.
  5. The firewall is blocking the port.
Show answer and explanation

Correct answer: B, E

B. The Unified Communications zone is down. E. The firewall is blocking the port. Port 8443 on Expressway-E can become unreachable due to firewall rules blocking the port at the network perimeter, preventing external access entirely. Additionally, the Unified Communications zone on Expressway-E may be down, causing the service listening on port 8443 to be unavailable even if the port is open.

Why the other options are wrong

  • A. The MRA license affects feature availability but does not prevent port accessibility.
  • C. Transform configuration relates to traffic processing, not port reachability.
  • D. The SRV record for _cisco-uds affects DNS service discovery but not the reachability of an already-known port.

Question 8

Which media encryption mode can be configured on an Expressway zone?

  1. Advanced Encryption Standard
  2. IPsec
  3. Triple Data Encryption Standard
  4. force unencrypted
Show answer and explanation

Correct answer: D. force unencrypted

Expressway zones support encryption modes including force encrypted and force unencrypted, where force unencrypted is a configurable option to mandate unencrypted media for specific zones. The options presented reflect Expressway's available media encryption settings rather than standard encryption algorithms.

Why the other options are wrong

  • A. AES is an encryption algorithm but not a selectable media encryption mode on Expressway zones.
  • B. IPsec is a network protocol, not a zone-level media encryption mode on Expressway.
  • C. 3DES is an encryption algorithm but not a configurable media encryption mode on Expressway zones.

Question 9

What is the purpose of a transform in the Expressway server?

  1. A transform has the function as a neighbor zone in the Expressway. It creates a connection with another server.
  2. A transform changes the audio codec when the call goes through the Expressway.
  3. A transform is used to route calls to a destination.
  4. A transform changes an alias that matches certain criteria into another alias.
Show answer and explanation

Correct answer: D. A transform changes an alias that matches certain criteria into another alias.

criteria into another alias. A transform in Cisco Expressway is a rule-based mechanism that matches incoming aliases against specified criteria and converts them into different aliases for routing purposes. Transforms are commonly used to normalize dial strings, convert between different addressing schemes, or adapt aliases based on patterns, making them essential for call routing and interoperability in unified communications environments.

Why the other options are wrong

  • A. A neighbor zone creates direct connections between Expressway servers; transforms are alias manipulation rules, not zone types.
  • B. Audio codec conversion happens at the endpoint or media processing level, not through transforms.
  • C. Transforms modify aliases; routing decisions are made by routes and search rules, not transforms.

Question 10

An organization with a domain name of example.com.

Which two SRV records are valid for a SIP and H.323 communication? (Choose two.)

  1. _sips._tcp.example.com
  2. _sips._udp.example.com
  3. _h323ls._udp.example com
  4. _h323ls._tcp.example.com
  5. _collab-edge._tls.example.com
Show answer and explanation

Correct answer: A, C

A. _sips._tcp.example.com C. _h323ls._udp.example com _sips._tcp.example.com is a valid SRV record for secure SIP over TCP. _h323ls._udp.example.com is a valid SRV record for H.323 location services over UDP. These records enable clients to discover appropriate services for their respective protocols within the example.com domain.

Why the other options are wrong

  • B. SIPs (SIP Secure) uses TCP, not UDP, as its transport protocol in standard SRV record definitions.
  • D. H.323 location services use UDP, not TCP, for SRV record queries.
  • E. _collab-edge._tls is not a standard SRV record type for SIP or H.323 communication protocols.

That was 10 of 277.

The full Cisco 300-820 CLHCT pack has all 277 questions, each with the answer, the explanation and why the other options are wrong, plus a questions-only copy for timed runs. US$39, paid once, with free monthly updates and a pass-or-your-money-back guarantee.

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