7• With Rx flow mode generic control enabled, an interface can receive flow control frames, but itcannot send flow control frames. When the interface receives a flow control frame from its peer, itsuspends sending packets to the peer. When congestion occurs, the interface cannot send flowcontrol frames to the peer.To handle unidirectional traffic congestion on a link, configure the flow-control receive enable commandat one end and the flow-control command at the other end. To enable both ends of a link to handle trafficcongestion, configure the flow-control command at both ends.To enable generic flow control on an Ethernet interface:Step Command Remarks1. Enter system view. system-view N/A2. Enter Ethernet interfaceview.interface interface-typeinterface-number N/A3. Enable generic flow control.• Enable TxRx mode genericflow control:flow-control• Enable Rx mode generic flowcontrol:flow-control receive enableBy default, generic flow control isdisabled on an Ethernet interface.Configuring PFC on an Ethernet interfacePFC performs flow control based on 802.1p priorities. With PFC enabled, an interface requires its peerto suspend sending packets with certain 802.1p priorities when congestion occurs. By decreasing thetransmission rate, PFC helps avoid packet loss.You can enable PFC for certain 802.1p priorities at the two ends of a link. When network congestionoccurs, the local device checks the PFC status for the 802.1p priority carried in each arriving packet. Thedevice processes the packet depending on the PFC status as follows:• If PFC is enabled for the 802.1p priority, the local device accepts the packet and sends a PFC pauseframe to the peer. The peer stops sending packets carrying this 802.1p priority for an interval asspecified in the PFC pause frame. This process is repeated until the congestion is removed.• If PFC is disabled for the 802.1p priority, the local port drops the packet.To configure PFC on an Ethernet interface:Step Command Remarks1. Enter system view. system-view N/A2. Enter Ethernet interface view. interface interface-typeinterface-number N/A3. Enable PFC on the interfacethrough automatic negotiationor forcibly.priority-flow-control { auto |enable } By default, PFC is disabled.4. Enable PFC for specific802.1p priorities.priority-flow-control no-dropdot1p dot1p-listBy default, PFC is disabled for all802.1p priorities.
