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Difficulty: MediumIP Addressing Services

An infrastructure team is deploying Voice over IP (VoIP) telephony across a corporate network. To ensure IP phones can dynamically discover the target hostname, listening port number, and transport protocol of the primary SIP server via domain queries, which DNS resource record type must be provisioned in the internal DNS zone?

  1. SRV recordAnswer
  2. B
    PTR record
  3. C
    CNAME record
  4. D
    MX record

Answer

The SRV record must be provisioned because it includes host, protocol, and port details required for service discovery.
The SRV record (Service Location record) is specifically formatted (e.g., _sip._tcp.example.com) to specify the location of servers for specified services, including the target domain name, port number, priority, and weight.

Step-by-Step Solution

1
Identify the operational requirement for client endpoint discovery.
IP phones require locating a specific service (SIP) along with its associated transport protocol (e.g., UDP/TCP) and port number (e.g., 5060).
Standard host resolution records only map names to IP addresses without service port context.
2
Evaluate standard DNS record capabilities against service discovery requirements.
Only an SRV (Service Location) record contains fields for service name, protocol, priority, weight, port, and target host.
SRV records are explicitly designed to allow clients to locate services operating on non-standard ports or specific server instances.

Key Concept

DNS SRV Record for Service Location
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Topics

IP Addressing Services

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