The largest and most complex of network types is the enterprise network. These networks are found around the world in the offices of multinational corporations. While a company may have a main corporate headquarters, the network itself may have more than one data center, acting as a regional hub. The data centers would be connected to one another using some form of high-speed WAN; in addition, numerous lower-speed spoke networks radiate from each hub, connecting branch offices, SOHO telecommuters, and traveling employees. The reliance on computer networks creates some serious challenges for today’s corporations.

Network reliability and security are essential, particularly when connected to the Internet. Companies must be willing to make significant investments in hardware, software, and people to achieve these goals. Not doing so could be fatal. As with the medium-sized company, large company networks use a variety of LAN technologies. The most common technology is Ethernet, but other technologies may be found, including Token Ring and Fiber Distributed Data Interface (FDDI). Unlike smaller companies, the large corporate network most likely evolved through the years as technology matured, and as mergers, acquisitions, and new branch offices added new network. segments. As such, the enterprise network could best be conceived as many different LAN technologies connected by WAN links. Below Figure shows the enterprise network with hubs and firewalls in place.

Many different networking protocols are likely in the corporate network, particularly in older more established companies. They will be supporting many legacy applications and protocols alongside the IP suite. In short, the network is a microcosm of the Internet as a whole, except under the administrative control of one or more IT professionals. The enterprise network topology is complex. Typically, the WAN links between the hubs of the network will be engineered to operate as a high-speed and reliable backbone connection. Each part of the hub network operates as a transit network for the backbone as well. This means that data from one remote office to another remote office will be routed through one or more hubs. This backbone network may be so large and so well engineered that the hubs will also serve as transit networks for information from other corporations. Since the enterprise network is composed of many hubs, branch offices, and SOHOs, the internal LAN topology will resemble that of the branch office closely. Information from the backbone will be distributed to the edges of the network and from there will access the LANs in a hierarchical fashion. One remote office sending traffic to another remote office must do so through the backbone because the offices do not share a direct connection.

Because of the complexity, size, and importance of the information on the network to the financial health of the company, staff will be devoted solely to network security on the enterprise network. Users will be strictly policed through the use of passwords, internal firewalls, and proxy servers. Network usage such as e-mail and Web access will be monitored, and well-defined and strict network security polices will be in place and enforced on a regular basis. While branch offices may have a person responsible for the security of that network under guidelines from the main office, some sort of network operations center will monitor the health and security of the network full time from a central location. Firewalls, proxy servers, and intrusion detection hardware and software will also be in use throughout the network to help provide network security. To protect communications between hubs and between the remote branch or SOHO user, VPN devices will also be employed. Physically, the network will be secured as well, and access to servers and workstations will be controlled by locks and identity checks whenever possible.