ISA modem in an A2000

[Tension]

I don't think this is going to work and anyway, modems are no longer a viable way of connecting two computers. You would be better off with ethernet or a serial cable.

Agreed.

A serial cable and ProNET are what you want.

http://aminet.net/comm/net/ProNET34.lha

Good luck!

[Tension]

The docs state a Keyfile (.key) is required for ProNET. Does anyone have a keyfile available?

The author made it freeware some years ago.  Do a bit of research on it.