The first thing we need to do is install an additional Network Interface Card (NIC) and allocate an IP address for it. We have already seen that each interface connected to the network requires an IP address, and we also know that these addresses need to be unique. This rule extends to any TCP/IP connection—it must not clash with any machine already out there.
So, how do we choose what address to assign it? Either an ISP or one of the naming authorities responsible for maintaining sanity among Internet users will probably allocate at least part of it. For example, we may be allocated a range of addresses from which we assign each one as we see fit, or we may be given an individual address.