Reference Guide

Interfaces | 241
Related
Commands
flowcontrol
Control how the system responds to and generates 802.3x pause frames on 10G and 40G stack units.
Syntax
flowcontrol rx {off | on} tx {off | on} threshold
Parameters
Defaults
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 MXL Switch.
The discard threshold should be larger than the buffer threshold so that the buffer holds at least hold at
least 3 packets.
On 4-port 10G stack units: Changes in the flow-control values are not reflected automatically in the
show interface output for 10G interfaces. This issue results from the fact that 10G interfaces do not
support auto-negotiation per-se.
Important Points to Remember
• Do not enable tx pause when buffer carving is enabled. Consult Dell Force10 TAC for information
and assistance.
• 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:
Cannot configure Asymmetric flowcontrol when speed <1G, config ignored
speed (for 1000/10000/auto interfaces) Sets the speed on the Base-T Ethernet interface.
negotiation auto Enables or disables auto-negotiation on an interface.
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.
Version 8.3.16.1 Introduced on MXL 10/40GbE Switch IO Module