How to Redirect All DNS Queries to OPNsense

My OPNsense installation runs AdGuard Home to filter advertisements and malicious websites, but many phone and computer applications hard-code external DNS servers such as Google DNS or 1.1.1.1. This can bypass AdGuard Home.

The following rule redirects all DNS queries to AdGuard Home (local DNS). Even when a client chooses another DNS server, queries sent over port 53 are redirected to OPNsense. This reduces DNS leaks and makes the local policy effective.

1. Open Firewall → NAT → Port Forward

2. Click + to add a rule

3. Configure the rule

Leave fields not listed above at their defaults.

4. Click Save and then Apply Changes

5. Open Firewall → Rules → LAN

6. Move the new rule above the default LAN allow rule

Click Apply Changes.

7. Test the result

For testing, I configured an AdGuard Home DNS rewrite for router.com to return 172.16.1.2.

 Screenshot

On a Windows PC:

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ipconfig /flushdns
nslookup router.com 8.8.8.8

Although the client asks 8.8.8.8, OPNsense redirects the DNS query to AdGuard Home, so the result should be 172.16.1.2.

Good luck 😉