How cachito labs Builds an OPNsense Firewall on ZimaBoard 2

Thanks to cachito labs for documenting this thoughtful ZimaBoard 2 project. In his original build video, an ISP problem becomes a practical lesson in routing, firewall policy, DNS privacy, and VPN egress. The useful idea is not simply to copy one configuration; it is to understand how a small dedicated computer can become the control point for an entire home network.

This walkthrough is especially useful if your ISP gateway gives you little control over routing or privacy. It follows the move from a provider-facing connection to a ZimaBoard 2 running OPNsense, then shows how firewall rules, DNS choices, and VPN routing change the network’s behavior. The sections below turn that build into a reusable decision guide rather than a timestamp-by-timestamp transcript.

Collaboration disclosure: The original video description includes an affiliate disclosure for products or services that may be referenced in the build. The article below summarizes cachito labs’ own configuration and intended use; software versions, interface details, hardware bundles, and compatibility may change after publication.

The result: ZimaBoard 2 Mini Home Server  is not a miniature replacement for a many-core rack server. Its strength is combining silent operation, dual 2.5GbE networking, direct SATA storage, and open PCIe expansion in a small x86 system that can be assigned one well-defined home-network role: a dedicated OPNsense firewall and routing appliance.

As you watch, focus on three connected changes: ZimaBoard 2 becomes the network gateway, OPNsense separates firewall and NAT policy from DNS behavior, and the VPN creates a different outbound identity for selected traffic. Those layers explain why the project can reduce ISP visibility without promising absolute anonymity.

When an ISP insists on controlling the edge device, the real loss is visibility and choice. A separate firewall restores both. ZimaBoard 2 sits between the provider connection and the rest of the home, while OPNsense decides which traffic is allowed, where it goes, and which services should resolve names or leave through a VPN. That separation makes the network easier to reason about and easier to change later.

Why an ISP Problem Became a Firewall Project

The build starts with a familiar home-network frustration: the provider does not want the customer’s own router at the edge. Instead of treating the ISP gateway as the brain of the network, cachito labs moves routing and policy onto hardware that the owner controls. The result is a clear boundary: the ISP supplies connectivity, while the local firewall owns the private network.

This distinction matters because an all-in-one gateway hides several jobs behind one interface. Routing, address translation, DNS forwarding, wireless access, and security rules may all be bundled together. A dedicated firewall exposes those jobs as separate decisions. You can replace the access point without replacing the router, send only selected devices through a VPN, or change DNS behavior without redesigning the whole LAN.

Why ZimaBoard 2 Fits the Firewall Role

A firewall does not need to look like a desktop PC. It needs dependable network interfaces, enough processing headroom for the selected services, and a physical form that can stay powered around the clock. ZimaBoard 2 is a compact x86 platform with dual 2.5GbE connectivity, making it a natural two-sided device: one port faces the ISP or upstream modem, and the other serves the internal switch.

The hardware is only the foundation. A dedicated edge box also changes the failure model. If it reboots or loses power, the whole home may lose connectivity, so the build should include a recovery plan: keep a known-good configuration backup, label both Ethernet paths, and make sure local administration remains possible when the WAN is unavailable. Small hardware is convenient, but it still deserves infrastructure-level care.

The Network Architecture Has to Be Correct Before Rules Matter

Before writing a firewall rule, draw the path a packet should take. The upstream interface receives the provider-side address, the downstream interface owns the private subnet, and every client uses the ZimaBoard 2 address as its default gateway. If those relationships are wrong, a perfect-looking rule set will not repair the topology.

That gateway position is what lets the firewall see traffic from every managed device. It can apply one policy to the whole household or more specific policies to VLANs, servers, workstations, and smart-home equipment. The design also makes troubleshooting more systematic: test the WAN, then the LAN gateway, then DNS, and only after that investigate application-level problems.

Installing OPNsense on a Dedicated Edge Device

Installing OPNsense on a small x86 computer is a practical way to turn generic hardware into a purpose-built router. The image is written to a bootable drive, the device starts from that media, and the installer places the operating system on its internal storage. Once the first boot completes, the console is used to assign the physical interfaces before the web dashboard takes over.

Interface assignment is the moment to slow down. A label such as “WAN” or “LAN” is only useful if it matches the actual cable and port. Confirm the link state, connect one side at a time, and keep the initial layout simple. Later, additional networks and services can be added without guessing which physical interface carries them.

Interfaces, Gateways, NAT, and the First Working Route

With the interfaces assigned, OPNsense needs an upstream gateway and a private LAN address. The LAN address becomes the default route for clients, while the WAN gateway points toward the ISP equipment. Address translation then allows private clients to share the upstream connection, which is the normal pattern for a home network behind one public address.

At this stage, verify basic connectivity before adding privacy features. A client should receive an address, reach the firewall dashboard, resolve a test name, and reach the public internet. Testing these layers separately prevents a VPN or DNS change from obscuring a simpler cabling, DHCP, or gateway mistake.

Firewall Rules and DNS Privacy Are Different Layers

Firewall rules answer “which traffic is allowed?” NAT answers “how does private traffic share the upstream address?” DNS settings answer “which resolver handles a name lookup?” These controls interact, but they are not interchangeable. Allowing outbound traffic does not encrypt DNS, and selecting an encrypted resolver does not automatically send all application traffic through a VPN.

A sensible baseline is to permit established return traffic, allow only the outbound services the network needs, and keep administration reachable from a trusted management segment. DNS can then be directed to a chosen resolver, with encrypted transport enabled where supported. The goal is not a magical “invisible” network; it is a smaller and more deliberate set of parties that can observe or influence each layer.

Routing Through a VPN Changes the Egress Identity

The VPN portion of the project changes the network’s exit path. Instead of sending selected traffic directly to the ISP, OPNsense establishes a tunnel and routes matching clients or destinations through it. External services then see the VPN provider’s egress address rather than the household’s usual public address.

That improves separation from the ISP, but it is not the same as total anonymity. The ISP can still observe the connection to the VPN service and broad traffic characteristics. The VPN provider becomes another point of trust, and websites can still identify users through accounts, cookies, browsers, or device fingerprints. Good policy therefore starts with a precise question: which traffic needs a different egress, and why?

A 3D-Printed Case and Rack Placement Make the Build Usable

The physical enclosure is more than decoration. A case protects the board, keeps the Ethernet paths stable, and makes it easier to mount the firewall where the modem and switch already live. A rack position also encourages a clean separation between the edge device, wireless access points, storage, and other servers.

Leave room for airflow and service access, especially if the board will run continuously. Mark the power adapter and both network cables, and avoid placing the firewall where a single accidental tug can disconnect the WAN. A compact network appliance is successful when it remains understandable six months after the initial build.

What This Setup Hides—and What It Does Not

Putting OPNsense on ZimaBoard 2 can hide the internal shape of the home network from the ISP. The provider no longer needs to manage each private client individually; from the outside, the edge firewall presents a controlled boundary. DNS choices and VPN routing can reduce the amount of destination information exposed through the default path.

Those benefits have limits. The ISP still provides the physical link, can see that the connection is active, and may identify the VPN endpoint or other metadata. The firewall cannot protect a compromised client, stop tracking performed by a logged-in service, or guarantee that every application obeys the intended route. Treat the project as network control and segmentation, not as a promise of absolute privacy.

Who Should Build a ZimaBoard 2 OPNsense Firewall?

This design is a strong fit for a technically curious household that wants control over routing, DNS, VPN policy, and future segmentation without buying a large enterprise appliance. It is also useful for a lab where several services need predictable networking and the owner wants to understand the path each packet takes.

It is less suitable when the priority is zero maintenance. A managed gateway may be the better choice for someone who does not want to maintain updates, backups, certificates, VPN credentials, and recovery procedures. For everyone else, the combination of a low-power board and a transparent firewall platform offers a practical middle ground between an ISP box and a full rack server.

Final Takeaway

cachito labs’ project shows why a small computer can have an outsized effect on a home network. ZimaBoard 2 supplies the compact, dual-interface platform; OPNsense supplies the policy engine; and the owner decides how DNS, NAT, firewall rules, and VPN routes fit together. The most durable lesson is architectural: establish a correct gateway first, test each layer independently, then add privacy and routing features with a clear understanding of what each one can—and cannot—hide.

For a similar low-power edge build, explore ZimaBoard 2Mini Home Server . For firewall documentation, see the official OPNsense website. If you want to compare configurations and share your own home-server setup, join the ZimaSpace Discord community.