Ethernet technology has become much more advanced than local networks. It got rid of collisions, got full duplex and gigabytes of speed. Wider spectre of economically efficient decisions has allowed using Ethernet on main lines. Ethernet is a packet technology of computer networks. Ethernet standards define wire connections and electric signals on physical level, packet format and medium access control protocol on the channel level of the model OSI. Ethernet is mainly described by the standards IEEE 802.3. Based on some reasons, in addition to the main standard, a lot of producers recommend using other patented carriers. For example, in order to increase the distance between two points of a network, it is more reasonable to use fiver-optic cables. The majority of Ethernet-maps and other devices have support of some data rates. These devices use auto detection of speed and duplex in order to achieve the best connection. If auto detection does not perform properly, the speed adjusts accordingly, and the mode of half-duplex transmission switches on. For example, Ethernet hub 10/100 suggests that by using this it is possible to work based on the technologies such as 10BASE-T and 100BASE-TX. Also, Ethernet hub 10/100/1000 supports the standards, such as 10BASE-T, 100BASE-TX, and 100BASE-T.