What is a DNS SRV record?

There are several types of records - or Resource Records as they are called - in the Domain Name System (DNS). This page explains what the SRV record is and how it's used.

The purpose of a DNS SRV record

SRV stands for "service". The SRV records can be useful to help services auto-discover configuration or connection settings.

For example, a well-configured SRV record can help mailserver auto-determine the settings for POP3 or IMAP mailservers. Or it can help telephones determine the SIP details to connect to the voice-over-IP server.

The structure of a DNS SRV record

The SRV records contain a fairly complex structure, here's an example:

_sip._tcp.example.com. 86400 IN SRV 0 5 5060 sipserver.example.com.

There's several flags that can be provided to a SRV record:

<service>.<proto>.<host>          <TTL>   IN  SRV   <priority> <weight> <port> <target>

The first portion, everything before the TTL, is unique in this record that it also contains meta information about the service you're describing.

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