🛠 Premier réseau : Ethernet double gigabit, Wi-Fi optionnel et SSH

Objectives

Network the ROCK 3B and control it via SSH without a screen. Card specifics: two gigabit Ethernet ports (gmac0 + gmac1 in the mainline device tree) but no soldered Wi-Fi — wireless connectivity relies on an M.2 E-Key module you install yourself (Radxa advertises support up to Wi-Fi 6). One Ethernet port supports PoE with the Radxa 25 W HAT.

Hardware

• Radxa ROCK 3B running Radxa OS Debian (official image at docs.radxa.com/download)
• Ethernet cable + DHCP box/router; optionally an M.2 E-Key Wi-Fi/BT module
• PC with an SSH client; or a USB-C cable connected to the OTG port for the serial console (1,500,000 baud, the UART is routed over USB-C)

Complete code

# Ethernet — brancher le câble puis :
ip -br addr                        # eth0 (et eth1 si 2e câble) avec une IP
sudo ethtool eth0 | grep -i speed  # attendu : 1000Mb/s
sudo dmesg | grep -i -e gmac -e link

# Wi-Fi : N'EXISTE PAS en natif — vérifier la présence d'un module M.2 E-Key
lspci | grep -i network            # module PCIe vu ?
sudo apt install firmware-misc-nonfree   # selon la puce du module

# SSH côté carte (Radxa OS) :
sudo apt install openssh-server && sudo systemctl enable --now ssh
ip -br addr | awk '/eth/{print $2}'
# Côté poste client : ssh <utilisateur>@<IP>   — identifiants par défaut : voir
# les notes de publication de votre image Radxa OS (elles changent selon les versions)

Expected verification

ip -br addr shows an IPv4 address on eth0 (and eth1 if the second port is cabled); ethtool indicates 1000 Mb/s; SSH connects from a neighboring machine; ping -c3 1.1.1.1 reaches the Internet. Without an installed Wi-Fi module, no wlan0 interface appears: this is normal for this card.

Common errors

• On a non-Radxa image (DietPi, mainline Debian…), only one Ethernet port works due to an old bootloader (eth1: Failed to reset the dma on recent kernels): flash a recent U-Boot (mainline rock-3b-rk3568_defconfig or Radxa SPI image) before investigating further.
• Looking for wlan0 without having purchased an M.2 E-Key module: CNX already criticized this at launch, as accessories are not easy to find.
• Plugging into the wrong port for PoE: only the port near the USB stack is compatible, with the 25 W HAT.
• Silent serial console: the console port is the USB-C (USB-CDC) at 1,500,000 baud, not a classic 4-pin connector.
• Exposing SSH without having changed the default image password.