Without NICs? A computer needs some sort of connection to the network! I don't think you can do it.
The usual NIC is an Ethernet card or a wireless network card; neither of which should be very expensive. In the center of the star topology is either a hub or a switch. Better use a switch, if possible - it is more efficient.
A hub
Mainframe computers first used star topology
Star Topology
Without knowing a bit more about the context, probably "topology".Common network topologies are ring, star, bus and mesh.
Star Topology
The arrangement of computers on a network is called topology. It describes how the individual computers are connected to each other and to the network.examples of topology are Star topology, ring topology, mesh topology, bus topology.
There are number of LAN technologies and each technology is classified into a category according to its topology , two such topologies are star and ring topology. In star topology ,The hub accepts data from a sender and delivers it to receiver, there is no security in star topology . In Ring topology Computers are connected in a circle- the first computer is cabled with the second computer.
The most common LAN topology is that of a "star." In a star topology, each computer, or "node", is connected to a central hub. This is more reliable than a more classical "ring" topology, because a node failing will not bring down the entire network. A bus topology is arguably more reliable, but has poorer performance.
Mesh Topology... though if you use a beefy-enough machine in the middle, a Star topology might work.
Star
A star topology is a type of mathematical topology. Mathematical topology is essentially geometry without concern for distance. It asks questions such as for a given shape, (in the abstract sense) "what connects to what," "is it possible to reach point x from point y without passing through point z," and "are these two points connected at all?" A star topology is a type of topology where all the points (for example, computers in a computer network) are connected to a central point, but not directly to each other. Go to the following address to see several types of network topologies, including a star topology. http://scilnet.fortlewis.edu/tech/Network/Topologies.htm
It is a Client/Server system. The most common topology for this is a Star topology.