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valid and the output shows that pluggable media (optical cables) is inserted into these ports. This is a software limitation for
this release.
Layer 2 Flow Control Using Ethernet Pause Frames
Ethernet pause frames allow for a temporary stop in data transmission.
A situation may arise where a sending device may transmit data faster than a destination device can accept it. The destination
sends a pause frame back to the source, stopping the sender’s transmission for a period of time.
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 frame is defined by IEEE 802.3x and uses MAC Control frames to carry the pause commands. Ethernet pause frames
are supported on full duplex only. The only configuration applicable to half duplex ports is rx off tx off.
NOTE: If a port is over-subscribed, Ethernet Pause Frame flow control does not ensure no loss behavior.
The following error message appears when trying to enable flow control when you already configured half duplex: Can’t
configure flowcontrol when half duplex is configure, config ignored.
The following error message appears when trying to enable half duplex and flow control configuration is on: Can’t
configure half duplex when flowcontrol is on, config ignored.
Enabling Pause Frames
Enable Ethernet pause frames flow control on all ports on a chassis. If not, the system may exhibit unpredictable behavior.
NOTE: If you disable rx flow control, Dell Networking recommends rebooting the system.
The flow control sender and receiver must be on the same port-pipe. Flow control is not supported across different port-pipes.
(also refer to iSCSI Optimization: Operation).
NOTE:
After you disable DCB, if link-level flow control is not automatically enabled on an interface, to enable flow control,
manually shut down the interface (shutdown command) and re-enable it (no shutdown command).
To enable pause frames, use the following command.
● Control how the system responds to and generates 802.3x pause frames on 10 Gig ports.
INTERFACE mode
flowcontrol rx [off | on] tx [off | on] [negotiate] [monitor session-ID]
○ 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.
○ negotiate: enable 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 sesssion-ID: enter the keyword monitor then the session-ID to enable mirror flow control frames on the
interface. The range is from 0 to 65535.
The default is rx off.
Interfaces
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