WAN port config in Linux

[Anonymous]

I am using Arch with lynix’s linux-aarch64-lts kernel.

I find that I cannot get the WAN port (eth2) to use the RJ45 reliably. Sometime it works, most of the time it does not – no lights, no link.

I think this is down to it choosing to look for a (not-installed) SFP card.

How can I configure the underlying eth2 device to look for the copper connection on the RJ45, and stay configured that way after a reboot?

Thanks in advance!

[Anonymous]

Answering my own question – I am using systemd-networkd, and it is really picky 😉
Once you nail down the config, its fine.

[dhliu]

1. See the ethernet block diagram here,
https://espressobin.net/mochabin_wiki/tiki-index.php?page=Block+diagram

2. see also the ports and interfaces photo here,
https://espressobin.net/mochabin_wiki/tiki-index.php?page=Ports+and+Interfaces

(a) Eth0 is 10Gb SFP+ optical WAN port
(b) Eth2 1Gb SFP optical WAN port share with RJ45 both came from the Gb PHY chip.
The PHY is configured to check which of the SFP and RJ45 ports is cable connected then assign it as the WAN port. The SFP port will be selected if both cables are connected.
(c) Eth0 and eth2 are networks bonded in mode-1(active backup) as the same WAN port with eth2 set to bond-primary. This means eth0 will be active only when eth2 doesn’t exist or fails
(d) ETH1, 1Gb LAN0, LAN1, LAN2, LAN3 all come out of Gb eth switch chip

3. As default with ubuntu rootfs, see /etc/network/interfaces
4. The network setup may change with different distribution like Ubuntu, archlinux or OpenWrt

[Author]

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