An Ethernet standard that transmits at 100 Mbps. Called "Fast Ethernet" when first deployed in 1995 and officially the IEEE 802.3u standard, it is a 100 Mbps version of 10Base-T (10 Mbps Ethernet). Like 10Base-T, 100Base-T is a shared media LAN when used with a hub (all nodes share the 100 Mbps) and 100 Mbps between each pair of nodes when used with a switch. Most Ethernet adapters and switches are 10/100 devices, which support both 100Base-T and 10Base-T (see 10/100 adapter).

100Base-T, 100Base-T4 and 100Base-TX
100Base-T uses two pairs of wires in Category 5 UTP cable, while 100Base-TX requires two pairs in Category 6 cable. 100Base-T4 uses all four wire pairs in older Category 3 cables. See 10Base-T and 100Base-FX.

See 100Base-T.