Command Line Reference Guide

Interfaces | 549
flowcontrol
c e s
Control how the system responds to and generates 802.3x pause frames on 1Gig and 10Gig line cards.
Syntax
flowcontrol rx {off | on} tx {off | on} threshold {<1-2047> <1-2013> <1-2013>}
The threshold keyword is supported on C-Series and S-Series only.
Parameters
Defaults
C-Series: rx off tx off
E-Series: rx on tx on
S-Series: rx off tx off
Command Modes
INTERFACE
Command
History
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 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
3 packets.
rx on
Enter the keywords rx on to process the received flow control frames on this port. This is
the default value for the receive side.
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. This is the default value on the send side.
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.
threshold
(C-Series and
S-Series only
)
When tx on is configured, you can set the threshold values for:
Number of flow-control packet pointers: 1-2047 (default = 75)
Flow-control buffer threshold in KB: 1-2013 (default = 49KB)
Flow-control discard threshold in KB: 1-2013 (default= 75KB)
Version 8.1.1.0 Introduced on E-Series ExaScale
Version 6.5.1.9 and 7.4.1.0 Introduced on E-Series
Version 7.8.1.0 Introduced on C-Series and S-Series with thresholds