Okay, first assume that I am completely f*****g stupid BUT, desperate to understand subnet masking. I'm reading the MCSE TCP/IP guide (for some reason I enjoy it) and have reached the Subnet chapter.

I set up a l2tp over ipsec vpn for a mac os x client. I can connect fine and I get an address, but the subnet mask is wrong (and corresponds to the class..). If I manually set the IP address and ...