Chapter 1 Product Overview
Front-Panel Description
10/100 and 10/100/1000 Ports
The Fast Ethernet (10/100-Mbps) and Gigabit Ethernet (10/100/1000-Mbps) ports use standard RJ-45 connectors and Ethernet pinouts with internal crossovers. The maximum cable length is 328 feet (100 meters). 100BASE-TX and 1000BASE-T traffic requires twisted four-pair Category 5 cable. 10BASE-T traffic can use Category 3 or Category 4 cable.
Fast Ethernet ports operate at 10 or 100 Mbps in either full- or half-duplex mode. In full-duplex mode, two stations can send and receive traffic at the same time. Normally, 10-Mbps ports operate in half-duplex mode, which means that stations can either receive or send traffic.
You can configure interface speed on Fast Ethernet and Gigabit Ethernet ports. On Fast Ethernet ports, you can configure the duplex mode to full, half, or autonegotiate. On Gigabit Ethernet ports, you can configure ports to full-duplex mode or to autonegotiate; half-duplex mode is not supported.
The default setting is autonegotiate. At this setting, the port senses the speed and duplex settings of the attached device and advertises its own capabilities. If the connected device also supports autonegotiation, the switch port negotiates the best connection (that is, the fastest line speed that both devices support and full-duplex transmission if the attached device supports it) and configures itself accordingly.
10/100 Inline Power Ports
The 10/100 ports on the Catalyst 3550-24PWR switch provide protocol support for Cisco IP Phones and Cisco Aironet Access Points:
•Provide –48 VDC power to all Cisco IP Phones and Cisco Aironet Access Points
•Automatically detect a Cisco IP Phone or an access point that is connected
On a per-port basis, you can control whether or not a Catalyst 3550-24PWR 10/100 port automatically provides power when an IP phone or an access point is connected. There are two inline power settings for each 10/100 port: Auto and Never. When you select the Auto setting for inline power on a port, the port only provides power if an IP phone or an access point is connected to it. The Auto setting is the default. However, when you select the Never setting for inline power on a port, the port does not provide power even if a Cisco IP phone or an access point is connected to it.
100BASE-FX Ports
The 100BASE-FX ports use 50/125- or 62.5/125-micron multimode fiber-optic cabling. In full-duplex mode, the cable length from a switch to an attached device cannot exceed 6,562 feet (2 kilometers).
The 100BASE-FX ports operate only at 100 Mbps in either full- or half-duplex mode and do not support autonegotiation. The half-duplex mode is the default setting.
You can connect a 100BASE-FX port to an SC or ST port on a target device by using one of the MT-RJ fiber-optic patch cables listed in Table B-1 on page B-2.
Catalyst 3550 Switch Hardware Installation Guide
