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 <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.
697
Summary of Contents for Force10 Z9000
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