How to Set Up Split DNS Configuration on macOS for Specific Domains

Introduction

For someone who needs to direct traffic for specific domains to a particular server, setting up a split DNS configuration on macOS is a straightforward way to achieve this. Today, we’ll explore how to resolve all domains ending in .sf through a designated DNS server at 172.16.7.1.

What is Split DNS?

Split DNS is a configuration where DNS queries for specific domains are handled by a designated DNS server, while all other queries go through the default DNS settings. This setup is particularly useful in development environments or for internal network purposes.

Setting Up Split DNS on macOS

To set up a split DNS configuration on macOS, we’ll use the built-in resolver feature. Here’s how:

Step 1: Create a Resolver Directory

Open Terminal and create a directory for resolver if it doesn’t already exist:

bashCopy code

sudo mkdir -v /etc/resolver

Step 2: Create a Resolver File

In /etc/resolver/, create a file named sf:

bashCopy code

sudo nano /etc/resolver/sf

Add the following line to specify the DNS server:Copy code

nameserver 172.16.7.1

Save and exit the editor.

Step 3: Flush DNS Cache

Flush the DNS cache to ensure your changes take effect:

bashCopy code

sudo dscacheutil -flushcache sudo killall -HUP mDNSResponder

Testing Your Configuration

After setting up, test it with nslookup or dig:

bashCopy code

nslookup example.sf

The server should now point to 172.16.7.1.

Troubleshooting

If the DNS queries are still being resolved by the default server (like Google’s 8.8.8.8), here are some things to check:

• Correct File and Syntax: Ensure /etc/resolver/sf is correctly set up.
• Permissions: Verify the file’s permissions and ownership.
• Direct Testing: Query the DNS server directly with dig @172.16.7.1 example.sf.
• Network Connectivity: Confirm that 172.16.7.1 is reachable and correctly configured.
• Restart Network Services: Sometimes, toggling network services can help.
• Reboot: When in doubt, reboot!