CompTIA Network+ (N10-009)Network OperationsMedium
A company is deploying a SIP-based VoIP service and wants client devices to automatically discover the correct server hostname and port for SIP signaling over TCP. Which DNS record type should be published to support this automatic discovery?
- ATXT record
- BMX record
- CCNAME record
- DSRV record
Show answer & explanationAnswer & explanation
Correct answer: D. SRV record
An SRV (Service) record specifies the hostname, port, priority, and weight for a given service, allowing clients to locate services like SIP, LDAP, or XMPP automatically. MX records are only for mail routing, CNAME is a simple alias, and TXT holds arbitrary text data such as SPF records.
Why the other options are wrong
- A. TXT records store text strings (e.g., SPF, verification codes) but not service location data.
- B. MX records route email to mail servers and have no port/protocol fields for other services.
- C. CNAME only creates an alias to another hostname; it carries no port or priority info.
SRV Record
A DNS resource record that specifies the hostname, port number, priority, and weight for a specific service, enabling automatic service discovery.
- Format includes service, protocol, priority, weight, port, target
- Commonly used for SIP, LDAP, and Active Directory service discovery
- Differs from MX, which only handles mail routing
Memory trick: SRV = Service Reveals Vitals (host, port, priority).