2. Introduction With available IP network numbers rapidly becoming an endangered species, efficient use of this increasingly scarce resource is important. This document describes how to split a single IP network number up so that it can be used on several different networks. This document concentrates on C Class IP network numbers - but the principles apply to A and B class networks as well. 2.1 Other sources of information There are a number of other sources of information that are of relevance for both detailed and background information on IP numbers. Those recommended by the author are:- The Linux Network Administrators Guide. The Linux System Administration Guide. TCP/IP Network Administration by Craig Hunt, published by O'Reilly and Associates.