- The 21st century is an era that has been characterised by phenomenal growth in data rates at the local area network (intranet), extranet and the Internet.This trend has been pushed by the widespread deployment in organisations of “bandwidth-hungry” applications such as VoIP, security surveillance systems, video conferencing and streaming of multimedia content. Due to demand placed on network resources by these applications and services,physical layer cabling solutions have had to evolve to support faster, improved LAN technologies such as Gigabit Ethernet.Although new network architectures (such as Centralised Fibre networks) address current and long term demands of the modern networking environment, concerns have been raised about its cost viability. The key problem identified in this study was an inadequacy of suitable tools that aid decision making when estimating the cost of a network infrastructure project. Factors of importance in this regard were collected in a survey and used in development of a cost model. The model is aimed at being a tool to assist network planners in estimating LAN infrastructure costs. A network was designed based on two architectures – centralised fibre (allfibrenetwork) and hierarchical star (UTP for horizontal cabling and optical fibre for backbone cabling). Thereafter, cost of implementing these two architectures was calculated using the model. Based on the results computed from the cost model, the all-fibre network (centralised fibre architecture) was found to be more cost effective compared to the hierarchical star network.