Reverse dns

Reverse dns

Setting up Reverse DNS (rDNS) involves mapping an IP address back to a domain name, which is the opposite of forward DNS. This is primarily used in email server configurations to verify the legitimacy of an IP address and prevent email spoofing.

Steps to Set Up Reverse DNS:
1. Obtain Control of Your IP Address
VPS or Dedicated Server: If you're using a VPS or dedicated server from a hosting provider, you'll likely have access to your IP addresses. You can request reverse DNS setup via your provider.
Own IP Range (for larger businesses): If you have control over your IP range (i.e., if your company has a dedicated block of IPs from your ISP or a registry like ARIN), you can set up reverse DNS directly through your ISP or IP management system.


2. Contact Your Hosting Provider or ISP
rDNS can only be configured by the owner of the IP address, which is typically your hosting provider or ISP. Reach out to them and provide the following:
Your IP Address: The IP address you want the rDNS set for.
PTR Record: The fully qualified domain name (FQDN) that the IP address should resolve to.
Example request:

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Hello, I would like to request rDNS setup for the IP address 192.0.2.1 to point to mail.example.com.


3. Configure the PTR Record (If You Have Control)
Some hosting providers (like AWS, Linode, or DigitalOcean) allow you to configure your own PTR records through their control panel.
For example, in AWS:
Go to the Route 53 console.
Choose the Hosted Zone for your domain.
Create a new PTR (Pointer) record and map it to the IP address.


4. Verify the rDNS Setup
Once your ISP or hosting provider has set up the PTR record, you can verify the reverse DNS record using a tool like dig or nslookup:

Using dig:

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dig -x
Using nslookup:

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nslookup
You should see the PTR record pointing to the domain name you provided.

Important Notes:
rDNS for IPv4: You typically set up reverse DNS for individual IP addresses.
rDNS for IPv6: It’s often set up for a range of addresses.
Time for Propagation: Changes to DNS records, including reverse DNS, may take up to 24-48 hours to propagate fully across the internet.