auto MDI-X" which allow a link to be automatically established even if the port does not auto-negotiate. This may or may not be implemented on a given device, so occasionally a crossover cable may still be necessary when connecting auto MDI-X to MDI-X (hub or switch), especially when autonegotiation is deactivated. Newer routers, hubs and switches (including some 10/100, and all 1-gigabit or 10-gigabit devices in practice) use auto MDI-X for 10/100 Mbit connections to automatically switch to the proper configuration once a cable is connected. Gigabit and faster Ethernet links over twisted pair cable use all four cable pairs for simultaneous transmission in both directions. For this reason, there are no dedicated transmit and receive pairs, and consequently, crossover cables are never required for 1000BASE-T communication. The physical medium attachment sublayer (PMA) provides identification of each pair and usually continues to work over crossover cables as well, even if the pairs are unusually swapped, crossed, or if the polarity of a pair is unexpectedly inverted. See also system to correct inversions within a pair Media-independent interface (MII) References External links Diagram of non-automatic connections between MDI and MDIX devices Network architecture Network protocols Ethernet