How to Configure Split DNS (Split Horizon) in Technitium DNS Server

Split DNS, also known as Split Horizon DNS, allows you to return different IP addresses for the same domain depending on where the DNS request originates. This is useful when internal devices should access services using private IP addresses while external users continue to resolve the domain normally through public DNS.

Using the Split Horizon app in Technitium DNS Server makes this process simple and flexible.

What Is Split DNS?

With Split DNS, internal clients can resolve:

example.com → 192.168.1.50

while external users resolve:

example.com → Public IP Address

This approach eliminates the need for hairpin NAT and improves performance for locally hosted services.

Step 1: Install the Split Horizon App

1. Log in to the Technitium DNS Server web dashboard.
2. From the left sidebar, select Apps.
3. Open the App Store.
4. Locate the Split Horizon app.
5. Click Install.

Once installed, the app becomes available for DNS records.

Step 2: Create a DNS Zone

1. Navigate to Zones.
2. Click Add Zone.
3. Enter your domain name (for example, example.com).
4. Select Primary Zone as the zone type.
5. Click Add.

Your authoritative DNS zone is now ready for configuration.

Step 3: Configure Split Horizon Records

1. Under Zones, click Edit next to your domain.
2. Select Add Record.
3. Set the record Type to APP.
4. For Name, enter either:
   • @ for the root domain, or
   • a subdomain such as www, nextcloud, or plex.
5. In the App Name / URL field, select Split Horizon.

A JSON template will appear. Edit the JSON to define which client subnets should receive which IP addresses.

Example Configuration

{
  "192.168.1.0/24": "192.168.1.50",
  "10.0.0.0/8": "10.0.0.75"
}

In this example:

• Devices on the 192.168.1.0/24 network receive 192.168.1.50.
• Devices on the 10.0.0.0/8 network receive 10.0.0.75.

How Fallback Resolution Works

If a DNS request originates from an IP address that is not defined in the JSON configuration, the Split Horizon app simply allows the request to continue to the configured upstream DNS servers.

This means external users or unknown networks will still resolve the domain normally without requiring additional configuration.

Step 4: Remove Conflicting A Records

When using Split Horizon records, avoid creating traditional A records for the same host.

For example:

Do not configure both:

• An APP record using Split Horizon.
• A standard A record for the same hostname.

If both exist, the standard A record takes precedence and the Split Horizon logic will be bypassed.

Step 5: Verify Forwarders and Upstream DNS

Open:

Settings → Proxy & Forwarders

Ensure your upstream DNS servers are configured correctly. These forwarders handle requests that are not answered by your local Split DNS configuration.

Proper upstream configuration ensures:

• External domains resolve correctly.
• Undefined hosts continue to function normally.
• Split Horizon records coexist seamlessly with recursive DNS resolution.

Benefits of Split DNS

Implementing Split Horizon DNS provides several advantages:

• Faster access to local services.
• Eliminates hairpin NAT issues.
• Allows internal and external users to access the same domain name.
• Simplifies self-hosted environments.
• Provides flexibility for multiple VLANs and networks.

Example Use Cases

Split DNS is especially useful for:

• Home Assistant servers
• Nextcloud installations
• Plex Media Server
• Reverse proxies
• Internal web applications
• Multi-VLAN home labs

Final Thoughts

Technitium DNS Server’s Split Horizon app provides a powerful and elegant way to serve different DNS responses based on the client’s source network. By combining authoritative zones with subnet-based routing, you can maintain a single domain name while directing internal users to private addresses and allowing external users to resolve through public DNS.

With proper upstream DNS configuration and the removal of conflicting A records, Split Horizon DNS becomes an excellent solution for homelabs, self-hosted services, and enterprise environments.

Additional Resource

For a deeper look at recursive DNS configuration with Technitium DNS Server, watch:

“The Perfect Pi-hole Upgrade – Technitium Recursive DNS” Published: February 28, 2026

This video provides an excellent companion guide for combining authoritative zones with recursive DNS resolution.
https://www.youtube.com/watch?v=D1e-3ruBkqA Published by Jeff @Craft Computing.

There will be more articles for Technitium, when I learn the steps to configure certain things. I do also plan on doing a video. These will not be as technical as some of the folks out there do/are, I plan on trying them from a layman’s point of view. I hope they will help those of you at a partial technical perspective.