 A potential disadvantage is sensitivity to station failures (i.e., one failed station might break the ring). Also, problems in a ring network are difficult to isolate, and net- work reconfiguration disrupts the operation of the entire network. Star Topology In the star topology, all stations are connected by cable segments to a centralized component called a hub. Devices can communicate with each other only through the hub. The star topology offers centralized resources and management. The advan- tages of the star topology include ease of fault isolation, ease of bypassing and repairing faulty stations, and high cost-efficiencies. Also, it's much easier to modify or add new computers in a star network than to do SO in other topologies. Disad- vantages include the need for a lot of cable to interconnect all the stations and the potential for total network disruption if the central hub facility fails. There are a number of variations on star networks. The star bus, for instance, is a combination of the bus and star topologies. It involves several star networks linked together with linear bus trunks. The star ring, sometimes referred to as the star-wired ring, looks similar to a star bus, except that the hubs in the star ring are connected in a star pattern, and the main hub contains the actual ring. LAN Interconnection and Internetworking The realm of LAN interconnection devices offers a number of options, including hubs, LAN switches, virtual LANs (VLANs), bridges, routers, and IP switches. These options are described in the following sections. Hubs interconnect the wiring that is connected to workstations. They are a build- ing block of most networks, although these days, they have largely been replaced by LAN switches. There are three major types of hubs: Active-Active hubs regenerate and retransmit signals, just as a repeater does. Because hubs typically have 8 to 12 ports for network computers to connect to, they are sometimes called multiport repeaters. Active hubs require electrical power to run (that's why