Cisco 2950G 24 Software Configuration Guide - Page 240
Configuration Guidelines, Autonegotiation for the speed
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Configuring Switch Interfaces Chapter 9 Configuring the Switch Interfaces Note You cannot configure speed or duplex mode on Gigabit Interface Converter (GBIC) ports, but for certain types of GBICs, you can configure speed to not negotiate (nonegotiate) if the GBIC ports are connected to a device that does not support autonegotiation. These sections describe how to configure the interface speed and duplex mode: • Configuration Guidelines, page 9-12 • Setting the Interface Speed and Duplex Parameters, page 9-13 Note The CPE Ethernet port settings have special considerations and different default settings from the switch 10/100 ports. For this information, see the CPE device considerations in the "CPE Ethernet Links" section on page 10-5. Configuration Guidelines When configuring an interface speed and duplex mode, note these guidelines: • Ethernet ports set to 1000 Mbps should always be set to full duplex. • Gigabit Ethernet ports that do not match the settings of an attached device can lose connectivity and do not generate statistics. • If both ends of the line support autonegotiation, we highly recommend the default setting of autonegotiation. • When connecting an interface to a 100BASE-T device that does not autonegotiate, set the duplex mode to full or half to match the device, and set the speed to auto. Autonegotiation for the speed setting selects the correct speed even if the attached device does not autonegotiate, but duplex mode must be explicitly set. • When connecting an interface to a Gigabit Ethernet device that does not autonegotiate, disable autonegotiation on the switch and set the duplex and flow control parameters to be compatible with the remote device. • 100BASE-FX ports operate only at 100 Mbps and in full-duplex mode. • 1000BASE-SX ports operate only at 1000 Mbps and in full-duplex mode. • GigaStack-to-GigaStack cascade connections operate in half-duplex mode, and GigaStack-to-GigaStack point-to-point connections operate in full-duplex mode. • When Spanning Tree Protocol (STP) is enabled and a port is reconfigured, the switch can take up to 30 seconds to check for loops. The port LED is amber while STP reconfigures. Caution Changing the interface speed and duplex mode configuration might shut down and re-enable the interface during the reconfiguration. 9-12 Catalyst 2950 Desktop Switch Software Configuration Guide 78-14982-01
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