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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 9 Configuring the Switch Interfaces
Configuring 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.