Service Manual

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.
negotiate (Optional) Enter the keyword negotiate to enable the pause-negotiation with the
egress port of the peer device. If the negotiate command is not used, pause-
negotiation is disabled. 40 gigabit Ethernet interfaces do not support pause-negotiation.
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
• rx off
• tx off
Command Modes INTERFACE
Command History
Version Description
9.11(0.0) Added support for monitor session.
9.9(0.0) Introduced on the FN IOM.
9.6(0.0) Added support for the negotiate feature on the M I/O Aggregator.
9.2(0.0) Introduced on the M I/O Aggregator.
8.3.16.1 Introduced on the MXL 10/40GbE Switch IO Module.
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.
On 4–port 10G stack units: Changes in the flow-control values may not be reflected automatically in the show
interface output for 10G interfaces. This is because 10G interfaces do not support auto-negotiation.
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:
Cannot configure Asymmetric flowcontrol when speed <1G, config ignored>
• You cannot configure half duplex when the flow control configuration is on (default is rx on tx on). The
following error is returned: Cannot configure half duplex when flowcontrol is on,
config ignored
Interfaces
509