11-13
Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
78-11380-10
Chapter11 Configuring Interface Char act eristics Configuring Ethernet Interfaces
Use the no local speed and no local duplex interface configuration commands to return the interface to
the default speed and duplex settings. To return all interface settings to the defaults, use the default
interface interface-id interface configuration command.
Configuring Media Types for Gigabit Ethernet Interfaces on LRE Switches
On the LRE switches, use the media-type interface configuration command to configure the media type
for Gigabit Ethernet interfaces. You can enable or disable fiber-optic or copper (10/100 /100 0)
connections. You can also manually set the port to select an SFP connector or an RJ45 connector. Use
the no form of this command to return to the default setting of SFP-preferred. To configure media types,
use the media-type {auto-select | rj45 | sfp} interface configuration command.
For more information, refer to the command refer en ce f or th is re lea se.
Configuring IEEE 802.3z Flow Control on Gigabit Ethernet Ports
Flow control is supported only on the 10/100/1000, 1000BASE-SX, GBIC-module, and SFP-module
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 congesti on
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 f rame , t he r emot e 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 802.3z flow control w hen qua lity of se rvic e
(QoS) is configured on the switch. Before configuring flow control on an interface, make sure to return
to the default QoS settings listed in the “Default Standard QoS Configuration” section on page30-18.
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 flow control state for Gigabit Ethernet ports is receive off and
send desired.
These rules apply to flow control settings on the device:
•receive on (or desired) and send on: Flow control operates in both directions; both the local and the
remote devices can send pause frames to show link congestion.
•receive on (or desired) and send desired: The port can receive pause frames an d can sen d pause
frames if the attached device supports flow control.
•receive on (or desired) and send off: The port ca nn ot se nd pause frame s but can op erat e w it h an
attached device that is required to or can send pause frames; the port can receive pause frames.
Step6 show running-config Display the LRE interface speed and duplex mode configuration.
Step7 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose