I have a lot of time trying to connect A1200 through different RTL8139 drivers.
Note at once: official driver from Elbox doesn't work for me because don't have chips update.
By using last 68k openpci_8139.device (1.2b1 and 1.22b4) with openpci.library 2.1beta4 68k (08.10.09) found an annoying bug hinder connection. Somewhere in the driver set wrong ARP ethertype.
It works the same for Genesis and MiamiDX 1.0c so I think on the driver.
Test the connection between the two network interfaces (AmigaOS and Debian), cross-over cable. I trying through different network cards in different Mediator PCI-slots not yet launched tcpdump and wireshark (preferable).
ping Linux -> AmigaOSsource: 78:54:2e:6f:8e:67
dest.: Broadcast
Protocol: ARP
0000 ff ff ff ff ff ff 78 54 2e 6f 8e 67 08 06 00 01 ......xT .o.g....
0010 08 00 06 04 00 01 78 54 2e 6f 8e 67 c0 a8 02 01 ......xT .o.g....
0020 00 00 00 00 00 00 c0 a8 02 02
ping AmigaOS -> Linuxsource: 00:4c:3c:10:4e:98
dest.: Broadcast
Protocol: 0x0608 (unknown)
0000 ff ff ff ff ff ff 00 4c 3c 10 4e 98 06 08 01 00 .......L <.N.....
0010 00 08 04 06 01 00 00 4c 3c 10 4e 98 a8 c0 02 02 .......L <.N.....
0020 00 00 00 00 00 00 a8 c0 01 02 b5 56 b5 56 b5 56 ........ ...V.V.V
0030 b5 56 b5 56 b5 56 b5 56 00 00 00 00 00 00 00 00 .V.V.V.V ........
ARP has hexadecimal protocol code the ethertype 0x0806
openpci_8139.device sends nonexistent code 0x0608!
Normal ethertype from Debian 7.0
Wrong ethertype from Miami DX 1.0c
Wrong ethertype from Genesis