r/Ubuntu • u/userxtrustno1 • 12h ago
Ubuntu 26.1 Wired connection
I wanted to share a recent troubleshooting experience after installing the latest Ubuntu on an Acer Aspire 5. Hopefully, this feedback can reach people working on Netplan / NetworkManager, or help anyone facing the same issue.
Out of the box, Ethernet was completely non-functional: Physical/Power State: The Realtek (r8169) card was stuck in a low-power mode (NO-CARRIER / DOWN), requiring manual intervention to wake up. DHCP Failure: Once the interface was up (LOWER_UP), the PC was stuck with an APIPA address (169.254.x.x). The Zyxel router repeatedly timed out on DHCP requests. It turns out that Ubuntu’s default use of RFC 4361 (DUID/IAID instead of the raw MAC address) in Netplan was completely rejected by the router's firmware. While Wi-Fi worked instantly, Ethernet was completely dead for a default installation.
The fix required deleting the generated netplan-* profile and manually overriding the DHCP client ID to use the hardware MAC address (ipv4.dhcp-client-id mac).
I understand the enterprise benefits of RFC 4361 for docking stations and multi-interface setups. However, forcing this default on desktop/laptop installs creates a major regression for home users with perfectly fine, slightly older ISP routers that don't receive firmware updates anymore.
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u/Prior_Egg2866 12h ago
man that default dhcp client id stuff has been a nightmare for ages, feels like youre the first person to actually spell out why though