Dell Force10 Z9000 FTOS Command Line Reference Guide for the Z9000 System FTOS - Page 697

Usage Information The globally assigned 48-bit Multicast address 01-80-C2-00-00-01 is used to send and receive pause frames. To allow full duplex flow control, stations implementing the pause operation instruct the MAC to enable the reception of frames with a destination address equal to this multicast address. The pause: • Starts when either the packet pointer or the buffer threshold is met (whichever is met first). When the discard threshold is met, packets are dropped. • Ends when both the packet pointer and the buffer threshold fall below 50% of the threshold settings. The discard threshold defines when the interface starts dropping the packet on the interface. This may be necessary when a connected device does not honor the flow control frame sent by the S-Series. The discard threshold should be larger than the buffer threshold so that the buffer holds at least hold at least three packets. Changes in the flow-control values may not be reflected automatically in the show interface output. As a workaround, apply the new settings, execute shut followed by no shut on the interface, then check the running-config of the port using the show interface command. Important Points to Remember • Do not enable tx pause when buffer carving is enabled. For information and assistance, consult Dell Force10 TAC. • Asymmetric flow control (rx on tx off, or rx off tx on) setting for the interface port less than 100 Mb/s speed is not permitted. The following error is returned: Can't configure Asymmetric flowcontrol when speed