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What is DNS Custom?

Published in DNS Configuration 3 mins read

Custom DNS enables users to specify the IP addresses of the DNS servers they want to use for performing reverse DNS lookups. Essentially, it allows you to override the default DNS servers used by a system or service with your own preferred DNS resolvers.

In more detail, custom DNS allows you to:

  • Specify DNS Servers: Instead of relying on the default DNS servers provided by your Internet Service Provider (ISP) or operating system, you can choose and configure your own.
  • Reverse DNS Lookups: Custom DNS specifically focuses on reverse DNS lookups, which translate IP addresses back into domain names. This is often used for verification, logging, and security purposes.
  • Gain Control: This offers more control over the DNS resolution process, potentially improving speed, reliability, and security.

Why Use Custom DNS?

  • Privacy: Avoid using your ISP's DNS servers, which may be subject to logging or censorship. Instead, you can use privacy-focused DNS providers.
  • Speed: Some custom DNS servers offer faster resolution times than default options.
  • Security: Use DNS servers with built-in security features, such as malware blocking and phishing protection.
  • Customization: Tailor DNS settings to meet specific needs, such as filtering content or using internal DNS servers.
  • Bypass Restrictions: In some cases, custom DNS can be used to bypass geographically-restricted content or censorship.

How it Works (Reverse DNS lookups)

Reverse DNS lookups typically rely on the PTR (Pointer) record in the DNS system. When you provide a custom DNS server and initiate a reverse lookup:

  1. The system queries your specified DNS server for the PTR record associated with a given IP address.
  2. The custom DNS server responds with the domain name (if one exists) associated with that IP address.
  3. If no PTR record is found, it usually returns NXDOMAIN (Non-Existent Domain).

Example Scenario:

Imagine you're running a mail server. You might want to use a custom DNS server for reverse DNS lookups to help verify that incoming email is legitimate and not spam. By using a reputable DNS server, you can more reliably confirm that the IP address sending the email matches the claimed domain name, thus improving your spam filtering accuracy.

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