Key takeaways
- Raspberry Pi OS or Debian with nftables: fully flexible, but you build and maintain everything yourself (firewall rules, DHCP, DNS, updates).
- Pi-hole or AdGuard Home alongside your existing router: if what you actually want is network-wide ad and tracker blocking, you do not need to replace the router at all.
A Raspberry Pi 5 can work as a capable firewall router for gigabit-class home internet if you run OpenWrt and add a second network port, but it cannot run pfSense at all, and once you add the extra hardware it needs, a small x86 or purpose-built OpenWrt box is often the simpler buy. This guide covers what the Pi 5 hardware actually gives you, which firewall software runs on it, and when a different device is the smarter choice.
The Pi 5 hardware realities that matter for routing
A router needs at least two network interfaces (one facing your modem or ONT, one facing your home network), a CPU that can handle NAT, firewall rules and possibly VPN encryption at line rate, and reliable storage and power. Here is how the Pi 5 lines up.
| Requirement | Raspberry Pi 5 | What it means for a router |
|---|---|---|
| CPU | Broadcom BCM2712, 4 x Cortex-A76 at 2.4 GHz | Plenty for NAT and firewall at 1 Gbps; VPN and traffic shaping eat into headroom |
| Built-in Ethernet | 1 x Gigabit | Only one port: you must add a second interface or use VLANs |
| USB | 2 x USB 3.0 (5 Gbps), 2 x USB 2.0 | A USB 3 Gigabit or 2.5GbE adapter can serve as the second port |
| PCIe | 1 x PCIe 2.0 x1 lane via FPC connector | NIC HATs can add a native Ethernet port; roughly 5 Gbps raw lane bandwidth |
| RAM options | 1, 2, 4, 8 or 16 GB | 2 GB is ample for OpenWrt; more helps only if you run containers or extras |
| Power | USB-C, 5 V; official supply rated 27 W | Use the official supply; undervoltage causes random network drops |
| Storage | microSD, or NVMe via a PCIe HAT | A router writes little, but a quality card or SSD avoids corruption after power cuts |
| Wi-Fi | Built-in dual-band Wi-Fi 5 radio | Weak as an access point; use a separate Wi-Fi 6 or Wi-Fi 7 access point |
The single biggest constraint is the lone Ethernet port. The PCIe lane is shared: if you use it for an NVMe HAT, you cannot also use a PCIe NIC HAT unless you buy a combined board.
Firewall software: what runs and what does not
OpenWrt: the practical choice
OpenWrt has official stable builds for the Pi 5 (the bcm27xx/bcm2712 target) in the 24.10 release line. You get a full router stack: firewall zones, DHCP and DNS, IPv6, WireGuard and OpenVPN, SQM traffic shaping with CAKE, ad blocking packages and a web interface (LuCI). It is the most direct path to a Pi-based firewall router.
pfSense: not an option on a Pi
pfSense releases are built only for 64-bit x86 (AMD64). Netgate’s own ARM appliances use custom builds that are not available for the Raspberry Pi, and there is no supported installer. Running pfSense in an emulated virtual machine on a Pi is technically possible but slow, and unsuitable for fast connections.
OPNsense: also an x86 product in practice
OPNsense is FreeBSD-based like pfSense. Its official images target x86 hardware; community ARM efforts exist but are not a dependable base for a home firewall on a Pi 5.
Other routes
- Raspberry Pi OS or Debian with nftables: fully flexible, but you build and maintain everything yourself (firewall rules, DHCP, DNS, updates).
- Pi-hole or AdGuard Home alongside your existing router: if what you actually want is network-wide ad and tracker blocking, you do not need to replace the router at all.
Adding the second port: three ways
| Method | Extra hardware | Pros | Cons |
|---|---|---|---|
| USB 3 Ethernet adapter | Gigabit (RTL8153 or AX88179 chip) or 2.5GbE (RTL8156) adapter | Cheap, easy, well supported by OpenWrt drivers | USB adapters can disconnect under heat or poor power; pick known chipsets |
| PCIe NIC HAT | A Pi 5 Ethernet HAT using the PCIe connector | Native PCIe interface, generally steadier than USB | Uses the only PCIe lane; adds cost and case constraints |
| Router on a stick (VLANs) | A managed switch that supports 802.1Q VLANs | No adapter; one cable carries WAN and LAN | WAN and LAN share 1 Gbps each way; needs switch configuration skills |
For most home builds, a USB 3 adapter with a Realtek RTL8153 (gigabit) or RTL8156 (2.5GbE) chip is the pragmatic choice. Install the matching driver package in OpenWrt before plugging it in, otherwise the second interface will not appear.
Setup outline with OpenWrt
- Flash the image. Download the Pi 5 factory image from the OpenWrt firmware selector and write it to a microSD card with a tool such as Raspberry Pi Imager or balenaEtcher.
- First boot on an isolated network. Connect a laptop directly to the built-in port; OpenWrt defaults to 192.168.1.1, which can clash with an existing router on the same subnet.
- Set a root password and update package lists. Then install the USB Ethernet driver for your adapter.
- Assign interfaces. Make the built-in port LAN and the USB adapter WAN, or the other way round; just be consistent and label the cables.
- Put the ISP device in bridge or passthrough mode to avoid double NAT, then connect it to the WAN port.
- Add a Wi-Fi access point. Connect any modern router in access point mode, or a dedicated access point, to a switch on the LAN side.
- Optional extras: SQM (CAKE) to tame bufferbloat, WireGuard for remote access, and an ad-blocking package.
- Back up the configuration from the System menu once it works; re-flashing a card takes minutes when you have a backup.
Cost reality: Pi build vs ready-made alternatives
Once you price the board, official power supply, case with cooling, storage, Ethernet adapter and a separate access point, a Pi 5 router is rarely the cheapest option. It wins on flexibility and fun, not on value.
| Option | Ports | Firewall software | Typical total cost | Best for |
|---|---|---|---|---|
| Raspberry Pi 5 + USB adapter | 1 x 1GbE + 1 x USB 1GbE or 2.5GbE | OpenWrt | Low to mid range, plus a Wi-Fi access point | Learners, tinkerers, spare Pi owners |
| GL.iNet Flint 2 (GL-MT6000) | 2 x 2.5GbE + 4 x 1GbE, Wi-Fi 6 built in | OpenWrt-based firmware, upstream OpenWrt supported | Mid range | OpenWrt features without the DIY hardware |
| Banana Pi BPI-R4 | 2 x 10G SFP+ + 4 x 1GbE | OpenWrt | Mid range (Wi-Fi 7 module extra) | Multi-gig fiber tinkerers |
| Fanless x86 mini PC (Intel N100/N150, 4 x 2.5GbE) | 4 x 2.5GbE, typically Intel i226-V | pfSense CE, OPNsense or OpenWrt x86 | Mid range, plus RAM and SSD in barebones kits | pfSense or OPNsense users, multi-gig WAN |
Which route fits you
- You own a spare Pi 5 and have gigabit or slower internet: build it with OpenWrt and a USB 3 adapter; it is a great way to learn routing.
- You specifically want pfSense or OPNsense: skip the Pi and buy a multi-port x86 mini PC.
- You want OpenWrt but also need reliable Wi-Fi in one box: an OpenWrt-friendly router such as the Flint 2 is simpler.
- You have 2 Gbps or faster fiber: the Pi’s single gigabit port and USB path become the bottleneck; go x86 or a board with 2.5G or 10G ports.
- You only want ad blocking: keep your router and add Pi-hole or AdGuard Home on the Pi instead.
Common mistakes
- Using a phone charger instead of the 5 V, 5 A official supply, then chasing “random” disconnects.
- Choosing an unknown-brand USB adapter whose chipset has no OpenWrt driver.
- Leaving the ISP gateway in router mode and ending up with double NAT, which breaks some gaming and VPN setups.
- Running without a heatsink or fan; a throttling CPU shows up as lower VPN and SQM throughput.
- Forgetting that a home firewall is now a single point of failure: keep the old router handy as a fallback.
