Securing the Family LAN: Dual DNS Filtering and VLAN Isolation with OPNsense and AdGuard Home

The Challenge of Digital Governance in the Smart Home

As architects of our own home labs, we often apply strict security rules at work but leave our family network vulnerable. Between chatty IoT devices, children’s consoles, and parents’ work laptops, the attack surface is massive. To secure the family’s digital life without degrading the user experience, a simple global WPA2 key is no longer enough. The solution? VLAN isolation combined with granular, dynamic DNS filtering.

Step 1: Network Segmentation (VLAN) on OPNsense

The first golden rule of security is compartmentalization. We will segment our network into three distinct zones using VLANs configured on our OPNsense router/firewall:

• VLAN 10 (Parents/Admin): Full access to the admin interface and the internet.
• VLAN 20 (Kids): Filtered internet access, zero communication allowed with VLAN 10 or the IoT network.
• VLAN 30 (IoT): Internet access restricted to the bare minimum, completely isolated from the rest of the network.

To do this, navigate to Interfaces > Other Types > VLAN on OPNsense. Create your interfaces, then define strict firewall rules in Firewall > Rules to block inter-VLAN traffic (especially from VLAN 20/30 to VLAN 10).

Step 2: Configuring AdGuard Home for Profile-Based Filtering

Instead of deploying multiple filtering servers, we will use the advanced features of AdGuard Home to apply customized security and parental control policies based on the client.

In the AdGuard Home UI, go to the Client Settings section. Here, you can add specific devices or entire subnets (such as the IP range of the Kids’ VLAN 20). For this « Kids » profile, enable:

• Block specific services (TikTok, YouTube restricted, Discord depending on age).
• Enforced SafeSearch on Google, Bing, and YouTube.
• Upstream DNS servers set to « Family Protection » (like Cloudflare 1.1.1.3).

Step 3: Blocking the Bypasses (Thwarting DNS Circumvention)

Kids are tech-savvy. If a child manually sets their DNS to 8.8.8.8 on their console or smartphone, they will bypass AdGuard Home. To prevent this, we must set up a NAT Port Forward rule on OPNsense.

Create a port redirection rule (DNAT) to intercept all outgoing queries on port 53 (UDP/TCP) that are not destined for your AdGuard Home IP, and forcibly redirect them to it. Do the same for port 853 (DNS over TLS) to block or redirect third-party secure DNS.

Conclusion

By combining the routing power of OPNsense and the flexibility of AdGuard Home, you achieve an enterprise-grade home network. Your personal data is isolated from potentially vulnerable smart devices, and your children’s browsing is protected seamlessly and centrally.