How many IP addresses using one network card?

only one ip address we can assign to a single NIC It varies depending on the operating system. DOS, likely just 1. Windows 2000, for example, can have at least hundreds of addresses assigned, but only 51 reliably work (51 total, spread out over all your nics, weather you have one or several). After the 52nd is added, Active Directory takes a dump and bad things happen. In Linux, it will vary by kernel version. Older kernels may be limited to 30 or so, whereas newer ones will be much higher. For the *BSD's, they'll generally handle more than Linux (and more efficiently), but I'm not sure what the actual limit is. Solaris on a 64 bit Sun platform probably would handle even more. I've heard of people running thousands and thousands of IP addresses in certain network simulation applications.