Deployment Guide

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 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.
If a port is over-subscribed, Ethernet Pause Frame flow control does not ensure no-loss behavior.
Restriction: Ethernet Pause Frame flow control is not supported if PFC is enabled on an interface.
Control how the system responds to and generates 802.3x pause frames on Ethernet interfaces. The default is rx off tx off.
INTERFACE mode. flowcontrol rx [off | on] tx [off | on]| [monitor session-ID]
Where:
rx on: Processes the received flow control frames on this port.
rx off: Ignores the received flow control frames on this port.
tx on: Sends control frames from this port to the connected device when a higher rate of traffic is received.
tx off: Flow control frames are not sent from this port to the connected device when a higher rate of traffic is received.
monitor session-ID: Enables mirror flow control frames on this port.
Changes in the flow-control values may not be reflected automatically in the show interface output. To display the change,
apply the new flow-control setting, shutdown the interface using the shutdown command, enable the interface using the no
shutdown command, and use the show interface command to verify the changes.
Enabling Pause Frames
Enable Ethernet pause frames flow control on all ports on a chassis or a line card. If not, the system may exhibit unpredictable
behavior.
NOTE:
Changes in the flow-control values may not be reflected automatically in the show interface output. As a
workaround, apply the new settings, execute shut then no shut on the interface, and then check the running-config of
the port.
NOTE: If you disable rx flow control, Dell EMC 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.
To enable pause frames, use the following command.
● Control how the system responds to and generates 802.3x pause frames on the Ethernet ports.
INTERFACE mode
flowcontrol {rx [off | on] tx [off | on] }
○ 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.
Configure the MTU Size on an Interface
If a packet includes a Layer 2 header, the difference in bytes between the link MTU and IP MTU must be enough to include the
Layer 2 header.
NOTE:
The system supports jumbo frames by default (the default maximum transmission unit (MTU) is 9416 bytes). To
configure the MTU, use the mtu command from INTERFACE mode.
For example, for VLAN packets, if the IP MTU is 1400, the Link MTU must be no less than 1422:
1400-byte IP MTU + 22-byte VLAN Tag = 1422-byte link MTU
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Interfaces