SRV Records | Configuring Host Records

SRV Records (Service Records) are used in DNS to specify the location of services within a domain. They provide information about the hostnames, ports, and priorities of services such as email, voice over IP (VoIP), and other network-based applications.

Structure of an SRV Record:

<service>.<protocol>.<domain> <TTL> IN SRV <priority> <weight> <port> <target>

• <service>: The name of the service, such as “sip” for SIP (Session Initiation Protocol) or “ftp” for FTP (File Transfer Protocol).
• <protocol>: The protocol used by the service, such as “tcp” or “udp.”
• <domain>: The domain name where the service is located.
• <TTL>: The time to live (TTL) for the record, specifying how long it should be cached by DNS servers.
• <priority>: The priority of the service, used for load balancing. Lower numbers have higher priority.
• <weight>: The relative weight of the service, used for load balancing. Higher weights have a higher chance of being selected.
• <port>: The port number on which the service is listening.
• <target>: The hostname or IP address of the server providing the service.

Example of an SRV Record:

_sip._tcp.example.com. 3600 IN SRV 10 1 5060 sip.example.com.

This SRV record specifies the location of a SIP service on the domain “example.com.” The service is listening on port 5060 of the server “sip.example.com.”

Uses of SRV Records:

• Email routing: MX records refer to SRV records to determine the specific mail servers responsible for handling email for a domain.
• VoIP services: SRV records are used to locate SIP servers and other components of VoIP systems.
• Custom services: SRV records can be used to define the location of any custom network-based service.

Troubleshooting SRV Records:

• Check DNS propagation: Ensure that changes to SRV records have propagated across the internet.
• Verify record accuracy: Verify that the SRV records contain the correct information, including the service name, protocol, port, and target.
• Use DNS tools: Tools like dig and nslookup can be used to query SRV records and troubleshoot issues.

By understanding SRV records and their role in DNS, you can effectively configure and manage network-based services, ensuring that they are accessible and function correctly.