Configuring Interface Characteristics
IEEE 802.3x Flow Control
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For information about which SFP modules are supported on your switch, see the product release notes.
•If both ends of the line support autonegotiation, we highly recommend the default setting of auto negotiation.
•If one interface supports autonegotiation and the other end does not, configure duplex and speed on both interfaces; do not use the auto setting on the supported side.
•When 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
IEEE 802.3x Flow Control
Flow control enables connected 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 by sending a pause frame to stop sending until the condition clears. Upon receipt of a pause frame, the sending device stops sending any data packets, which prevents any loss of data packets during the congestion period.
Note The switch ports can receive, but not send, pause frames.
You use the flowcontrol interface configuration command to set the interface’s ability to receive pause frames to on, off, or desired. The default state is off.
When set to desired, an interface can operate with an attached device that is required to send
These rules apply to flow control settings on the device:
•receive on (or desired): The port cannot send pause frames but can operate with an attached device that is required to or can send pause frames; the port can receive pause frames.
•receive off: Flow control does not operate in either direction. In case of congestion, no indication is given to the link partner, and no pause frames are sent or received by either device.
Note For details on the command settings and the resulting flow control resolution on local and remote ports, see the flowcontrol interface configuration command in the command reference for this release.
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