Specifications

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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 11 Configuring the Switch Interfaces
Configuring Switch Interfaces
Use the no speed and no duplex interface configuration commands to return the interface to the default
speed and duplex settings (autonegotiate). To return all interface settings to the defaults, use the default
interface interface-id interface configuration command.
This example shows how to set the interface speed to 10 Mbps and the duplex mode to half on Fast
Ethernet interface 0/3 and to verify the configuration:
Switch# configure terminal
Switch(config)# interface fastethernet0/3
Switch(config-if)# speed 10
Switch(config-if)# duplex half
Switch(config)# end
Switch# show running-config
Building configuration...
Current configuration : 1954 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Switch
!
<output truncated>
!
interface FastEthernet0/3
switchport mode trunk
no ip address
duplex half
speed 10
!
<output truncated>
Configuring IEEE 802.3X Flow Control on Gigabit Ethernet Ports
Flow control is supported only on the 10/100/1000, 1000BASE-SX, and GBIC ports. Flow control
enables connected Gigabit Ethernet ports to control traffic rates during congestion by allowing congested
nodes to pause link operation at the other end. If one port experiences congestion and cannot receive any
more traffic, it notifies the other port to stop sending until the condition clears. When the local device
detects any congestion at its end, it can notify the link partner or the remote device of the congestion by
sending a pause frame. Upon receipt of a pause frame, the remote device stops sending any data packets,
which prevents any loss of data packets during the congestion period.
Note We strongly recommend that you do not configure IEEE 802.3X flowcontrol when quality of service
(QoS) is configured on the switch. Before configuring flowcontrol on an interface, make sure to return to
the default QoS settings listed in the “Default Standard QoS Configuration” section on page 27-16.
Flow control can be implemented in two forms, symmetric and asymmetric. The symmetric
implementation is suitable for point-to-point links, and asymmetric is suitable for hub-to-end node
connections, where it is desirable for the hub to pause the end system, but not vice-versa. You use the
flowcontrol interface configuration command to set the interface’s ability to receive and send pause
frames to on, off, or desired. The default state for Gigabit Ethernet ports is receive off and send desired.
The default state for Fast Ethernet ports is receive off and send off.