Reference Guide

flowcontrol
Control how the system responds to and generates 802.3x pause frames on 1Gig and 10Gig line cards.
S4820T
Syntax
flowcontrol rx {off | on} tx {off | on}
Parameters
rx on Enter the keywords rx on to process the received flow control
frames on this port.
rx off Enter the keywords rx off to ignore the received flow control
frames on this port.
tx on Enter the keywords tx on to send control frames from this port to
the connected device when a higher rate of traffic is received.
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.
Defaults S4820T: rx on tx off
Command Modes INTERFACE
Command History
This guide is platform-specific. For command information about other platforms, refer to the
relevant FTOS Command Line Reference Guide .
The following is a list of the FTOS version history for this command.
Version 8.3.19.0 Introduced on the S4820T.
Version 8.3.11.1 Introduced on the Z9000.
Version 8.3.7.0 Introduced on the S4810.
Version 8.1.1.0 Introduced on the E-Series ExaScale.
Versions 6.5.1.9
and 7.4.1.0
Introduced on the E-Series.
Version 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
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