LDAP plugins on Win/IIS vs Linux/Apache

Good day, gurus. I’m setting up WordPress sites for a school division. As long as I set them up on the Windows server IIS(6) machine, I can use various active directory plugins to authenticate. But… that’s clearly not an ideal platform for WordPress. I’m also testing a Linux (Ubuntu) server, on which “everything just works” EXCEPT for active directory authentication.

I can certainly provide more details, but perhaps I’m just missing something basic that needs to be set up on the server so that it can “see” the active directory server.

Thanks for your consideration,

Nick.