I'm trying to setup Ethernet connection on Omnima A20 - it's a cheaper stripped down version of Cubietruck (less RAM, less IO connectors, RTL8201CP 100Mbit network chip instead of 1Gbit).
I'm using Debian Buster server image for Cubietruck. Everything works fine except Ethernet. ethtool says the link is up, full duplex 100Mbit. Neither networkmanager nor dhclient are able to obtain IP address from router. Static IP assignment (via /etc/network/interfaces or with "ip addr add/ip route add") succeeds, but router is unreachable for ping ("Destination Host Unreachable").
I've ruled out hardware failure:
Inserting the same cable into laptop produces working connection, both via DHCP and with static IP.
Rebooting the board into stock firmware (POS system based on Debian Wheezy) produces working connection for static IP at least. I didn't test the DHCP because original firmware goes out of its way to block any non-whitelisted usage scenario.
Router firmware and hardware are working correctly based on the tests above.
It seems that kernel detects NIC correctly (based on dmesg). Pinging the router ("Destination Host Unreachable") steadily increases TX bytes in ifconfig, RX stays at 0 all the time.
This is where my knowledge/google-fu ends. Do you have any ideas on how to troubleshoot/fix this issue? Thanks!