Users Guide

tx on: Sends control frames from this port to the connected device when a higher rate of trac is received.
tx off: Flow control frames are not sent from this port to the connected device when a higher rate of trac is received.
Changes in the ow-control values may not be reected automatically in the show interface output. To display the change, apply the
new ow-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 ow control on all ports on a chassis or a line card. If not, the system may exhibit unpredictable behavior.
NOTE: Changes in the ow-control values may not be reected 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-cong of the port.
NOTE: If you disable rx flow control, Dell Networking recommends rebooting the system.
The ow control sender and receiver must be on the same port-pipe. Flow control is not supported across dierent 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] [negotiate]
• rx on: enter the keywords rx on to process the received ow control frames on this port.
• rx off: enter the keywords rx off to ignore the received ow 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 trac is
received.
• tx off: enter the keywords tx off so that ow control frames are not sent from this port to the connected device when a
higher rate of trac 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.
• threshold: when you congure tx on, you can set the threshold values for:
• Number of ow-control packet pointers: the range is from 1 to 2047 (default = 75).
• Flow-control buer threshold in KB: the range is from 1 to 2013 (default = 49KB).
• Flow-control discard threshold in KB: the range is from 1 to 2013 (default = 75KB).
• Buer threshold limit for generating PAUSE frames: the range is from 1 to 4096.
• Oset value for generating PAUSE frames to resume trac: the range is from 1 to 4096.
Congure the MTU Size on an Interface
If a packet includes a Layer 2 header, the dierence in bytes between the link MTU and IP MTU must be enough to include the Layer 2
header.
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
The following table lists the various Layer 2 overheads found in Dell Networking OS and the number of bytes.
The following table lists the various Layer 2 overheads found in the Dell Networking OS and the number of bytes.
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Interfaces