Doesn't RA2 check serials over network?

I do remember having to install IPX to play over LAN.

The original release came with separate Allied/Soviet discs. You could put one in your buddy's computer.

Keygen was also easily available.

I don't think it did, or at least not the version I had, though it's entirely possible I am misremembering. I know for certain we did the same thing with StarCraft as well. Somehow, we got multiple instances of RA2 running on a LAN.