Usage
PTRrecords point services to instances of services (DNS-SD).PTRrecords point IP addresses to (sub)domains (rDNS).
Example for service enumeration (DNS-SD):
| Type | Name (use @ for root) | Priority | Weight | Port | Value | TTL |
|---|---|---|---|---|---|---|
| PTR | _app._tcp | foo._app._tcp | ||||
| PTR | _app._tcp | bar._app._tcp | ||||
| SRV | foo._app._tcp | 1 | 1 | 5333 | app.example.com. | |
| SRV | bar._app._tcp | 1 | 1 | 5333 | db.example.com. |
The app service has a foo instance and a bar instance.
Description
A PTR (Pointer) record points to a domain or service. A PTR record does not redirect or forward a query to resolve the domain or service provided in the PTR record. Instead, the DNS response simply returns the service name or domain name specified in the PTR record.
Use cases:
| Description | |
|---|---|
| DNS-SD | In DNS Service Discovery, PTR records are used to enumerate service instances for a given service type. |
| rDNS | In a reverse DNS (rDNS) lookup, a client requests the domain name associated with an IP address (for example via dnschecker.org or dig -x 203.0.113.1). A rDNS entry is usually set up by the provider who owns the IP address (see note below about Hetzner IPs). PTR records for rDNS are not added in the zone of the domain. Instead, they are added in a reverse zone (e.g. 1.113.0.203.in-addr.arpa.) that belongs to the owner of the IP.Allows mail servers to verify whether the sender's IP address is authorized to send emails on behalf of the domain. |
rDNS with Hetzner IPs
You should not create PTR records for IP addresses with Hetzner as those IPs already have PTR records managed by Hetzner. By default, the IP points to a domain that looks like this:
static.1.113.0.203.clients.your-server.deYou can edit the value as explained in these articles:
In Hetzner Console, you can edit the value by selecting your cloud server or Load Balancer and navigating to the "Networking" tab in the top menu bar. Replace static.<your_reverse_ip>.clients.your-server.de with your own domain that points to the IP address of that cloud server or Load Balancer. The PTR record managed by Hetzner is automatically updated accordingly. You can edit the reverse DNS of Primary IPs and Floating IPs as well.