Dell Force10 Z9000 Reference Manual page 697

Usage
The globally assigned 48-bit Multicast address 01-80-C2-00-00-01 is used to send and receive
Information
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:
The
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 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
either the packet pointer or the buffer threshold is met (whichever is met
• Starts when
first). When the discard threshold is met, packets are dropped.
both the packet pointer and the buffer threshold fall below 50% of the
• Ends when
threshold settings.
discard threshold defines when the interface starts dropping the packet on the interface.
• 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 <1G,
config ignored
• The only configuration applicable to half duplex ports is rx off tx off. The
following error is returned:
Can't configure flowcontrol when half duplex is
configure, config ignored
• Half duplex cannot be configured when the flow control configuration is on (default is
rx on tx on). The following error is returned:
Can't configure half duplex when flowcontrol is on,
config ignored
NOTE: The flow control must be off (rx off tx off) before configuring the half
duplex.
• Speeds less than 1 Gig cannot be configured when the asymmetric flow control
configuration is on. The following error is returned:
Can't configure speed <1G when Asymmetric flowcontrol is
on, config ignored
• FTOS only supports rx on tx on and rx off tx off for speeds less than 1 Gig
(Symmetric).
• On the C-Series and S-Series systems, the flow-control sender and receiver must be
on the same port-pipe. Flow control is not supported across different port-pipes on the
C-Series or S-Series system.
NOTE: If you disable rx flow control, Dell Force10 recommends rebooting the
system.
buffer threshold so that the
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