RouterPi – A Gigabit Ethernet Based Raspberry Pi Compute Module 4 Router

Zak Kemble enjoys building things and has been coveting different Raspberry Pi devices for several years with the hopes of using them as a router. Unfortunately, none of them have yet to deliver the raw throughput of the Gigabit Ethernet ports that he requires. When the Compute Module 4 arrived on the market,  set out to convert the CM4 module into a complete Gigabit Ethernet router. His great website details the project, and a link to GitHub provides access to the sources.

Of course, the Compute Module 4 is only a module; it's intended to be integrated into another product, which is one of the numerous differences between it and a standard Raspberry Pi. [Zak] created a two-layer PCB that separates the CM4's major functions. However, even if it's GbE, a router with only one Ethernet port isn't actually a router. [Zak] connected a Realtek RTL8111HS GbE controller to the PCIe bus to ensure that he could use the device's maximum bandwidth.

RouterPi Hardware Specifications

• Raspberry Pi Compute Module 4 with 2GB RAM & 8GB eMMC
• 2x Gigabit Ethernet interfaces (CM4 onboard & Realtek RTL8111HS)
• WiFi U.FL to SMA connector
• micro HDMI port
• micro-USB OTG port
• DS3231 RTC with battery backup
• BME280 Environmental sensor
• 12V to 5V regulator
• Buzzer
• Buttons for safe shutdown and restart/boot

The list of fancy additions is quite extensive, but it includes such nice hacks as the ability to power other network devices bypassing via the 12 V power supply, having a power off and hard reset button, and even incorporating an ambient sensor (though he doesn't explain why... but why not?).

Testing the RouterPi revealed some performance constraints, which were remedied by making some creative software changes that assigned different ports and duties to separate CPU cores. Overall, it's a nice-looking gadget that has served as a router, DNS resolver, and more—what more could you want from an experimental project?

This CM4-based project stands in stark contrast to Cisco's original network product, which was revolutionary in its own right but lacked Gigabit Ethernet.

Source - Zak's Electronics Blog