The Cisco Catalyst 4000/4500 Series 24-port 10/100/1000BASE-T line card provides 24 RJ-45 ports with triple speed auto-sensing and auto-negotiating technology, enabling all ports to be used at 10 Mbps, 100 Mbps, or 1000 Mbps up to 100 meters over Category 5 copper cabling. This module provides wiring closet investment protection by allowing Fast Ethernet desktops today to migrate to Gigabit Ethernet in the future without replacing the switch line cards. The 24 ports can burst to Gigabit Ethernet line rate and share 12 Gbps of capacity (6 Gbps full-duplex) into the switching fabric. The amount of oversubscription can be controlled by varying the number of ports used at 1000 Mbps. All ports can utilize Gigabit EtherChannel or IEEE 802.3ad for high-speed interconnection applications. All ports use the standard IEEE 802.1x flow control (PAUSE frame) mechanism to control Gigabit Ethernet host traffic.