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SRV Record (Service Record) (SRV Record)

Security Glossary - DNS

Definition: An SRV record specifies the hostname and port number of servers for specific services. Unlike A records that only provide IP addresses, SRV records include the port, priority, and weight, enabling DNS-based service discovery. They are used by protocols like SIP, XMPP, LDAP, and Microsoft Active Directory.

Why SRV Record Is Important

SRV records enable automatic service discovery, so clients can find the right server and port for a service without hardcoding connection details. For example, a SIP phone client can look up the SRV record for _sip._tcp.example.com to find the VoIP server's hostname and port.

The priority and weight fields in SRV records provide built-in load balancing and failover. Lower priority values are tried first, and weight distributes traffic among records with equal priority. This allows sophisticated traffic management purely through DNS configuration.

For web applications, SRV records are less commonly used since HTTP has its own service discovery mechanisms. However, if you run services like XMPP chat, CalDAV/CardDAV (calendar and contacts), or internal microservices that support SRV lookups, proper SRV record configuration is important for reliability and automatic failover.

How to Test for SRV Record

A DNS health checker can query SRV records for common services associated with your domain. Verify that the target hostnames are reachable and the port numbers are correct. Check priority and weight values if you use SRV for load balancing or failover.

Check DNS Health

Common Questions About SRV Record

Are SRV records used for web traffic?
Not typically. Web browsers use A/AAAA records to find web servers and HTTP headers for service information. SRV records are primarily used by other protocols like SIP, XMPP, and LDAP that were designed to use DNS-based service discovery.
What is the format of an SRV record?
The record name follows the pattern _service._protocol.domain (like _sip._tcp.example.com). The record value includes priority, weight, port, and target hostname. For example: 10 60 5060 sipserver.example.com.

See Also

Domain Name System A Record (Address Record) DNS Zone MX Record (Mail Exchange Record) Nameserver
Disclaimer: DomainOptic provides automated informational scans only. Results do not constitute professional security advice, compliance certification, or a guarantee of security. Always verify findings independently.