SRV records are DNS records that are used to specify the location of servers for specific protocols and domains. This can be thought of as a logical extension of what MX records provide. Whereas MX records are used only for routing email, SRV records can be used for any IP network service.
SRV records are also called "service records," or "service locator records," and are defined in RFC 2782.
DNS Check can monitor your SRV records, and notify you if they become unresolvable, or have any of their parameters change.
Fields
Here are the fields that make up an SRV record:
| Field | Description | Example |
|---|---|---|
| Service | The name of the service that the SRV record is for, prefixed by an underscore (_). | _x-puppet |
| Protocol | The name of the protocol that the SRV record is for, prefixed by an underscore (_). This is usually either "_tcp" or "_udp". | _tcp |
| Domain | The FQDN (fully qualified domain name) that the SRV record is for. | dnscheck.co. |
| Type | The DNS record type. Always set to "SRV". | SRV |
| Priority | The priority of the SRV record. The record with the lowest Priority value is considered the most desirable. This is similar to an MX record's Preference field. | 10 |
| Weight | Used to break a tie when two or more SRV records have the same priority. See RFC 2782 for details. | 5 |
| Port | The port that the service listens on. This is usually a TCP or UDP port. | 8140 |
| Target | The fully qualified domain name (FQDN) of the host that provides this service. | master-a.dnscheck.co. |
DNS Zone File Examples
Here's an example of how an SRV record which uses the example values from this page's Fields section looks in a DNS zone file:
; Name Type Priority Weight Port Target
_x-puppet._tcp.dnscheck.co. SRV 10 5 8140 master-a.dnscheck.co.
The Name ends in a period in the above example, so it's a fully qualified domain name.
Alternatively, you can create an SRV record that's relative to the zone file's $ORIGIN. Here's an example of how to do this using the example values from this page's Fields section:
$ORIGIN dnscheck.co.
; Name Type Priority Weight Port Target
_x-puppet._tcp SRV 10 5 8140 master-a
Additional Resources
- RFC 2782 - this RFC is dedicated to SRV records.