Administrator Guide

tx off Enter the keywords tx off so that flow control frames are not sent from this port to
the connected device when a higher rate of traffic is received.
pause-threshold Enter the keyword pause-threshold to configure the buffer threshold (in Kilobytes)
at which the interface starts transmitting pause frames for link-level flow control. Valid
values are 1 to 12480KB. The default is 60KB.
resume-offset Enter the keyword resume-offset to configure the buffer threshold (in Kilobytes) at
which the interface resumes transmitting offset frames for link-level flow control. Valid
values are 1 to 12480KB. The default is 9KB.
monitor Enter the keyword monitor then the session-ID to enable mirror flow control frames on
the interface. The range is from 0 to 65535.
Defaults An interface ignores flow-control frames received from other network devices (rx off) and does not transmit
pause frames (tx off).
Command Modes INTERFACE
Command History
This guide is platform-specific. For command information about other platforms, see the relevant Dell Networking
OS Command Line Reference Guide.
The following is a list of the Dell Networking OS version history for this command.
Version Description
9.11(0.0) Added support for monitor session.
9.9(0.0) Introduced on the C9010.
9.2(1.0) Introduced on the Z9500.
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.3.7.0 Introduced on the S4810.
8.1.1.0 Introduced on the E-Series ExaScale.
6.5.1.9/7.4.1.0 Introduced on the E-Series.
7.8.1.0 Introduced on the C-Series and S-Series with the thresholds option.
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 switch. 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 then 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
Networking 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:
Interfaces 677