Users Guide

Layer 2 Switching Commands 434
Command Mode
Interface Configuration (Ethernet) mode
User Guidelines
Not all interfaces are capable of supporting all speeds. Refer to the Hardware
Overview section of the Users Configuration Guide for a description of the
capabilities of a particular interface.
The speed command is only applicable to Ethernet ports. It gives an error if
used on stacking ports or port-channels.
Use the auto parameter to enable auto-negotiation on an interface. Auto-
negotiation on copper interfaces selects a clock master, performs link training
to tune the pre-emphasis settings to the individual switch and cable,
negotiates the internal media, and may enable a decision feedback equalizer
(DFE) to correct burst errors if the PHY has the capability. To disable auto-
negotiation on a port, it is necessary to enter the speed command without
using the auto parameter. Disabling auto-negotiation on 1G copper ports
may lead to random frame loss as the clock master and media have not been
arbitrated by the auto-negotiation process. Auto-negotiation is required on
2.5G/5G/10G/40G copper ports and is always recommended for copper ports
regardless of the speed setting. SFP+ ports utilizing a copper DAC cable are
considered copper ports. Auto-negotiation is also required on 1000Base-X
ports (including SFP fiber ports.)
If using combinations of the 10, 100, 1000, 2500, 5000, 10000, 25000, 40000,
50000, or 100000 keywords with the auto keyword, the port only advertises
the specified speeds. Not all speeds or combination of speeds are available on
all platforms or ports. Entering an unsupported speed will produce the
following error message An invalid interface has been used for
this function.
Fiber ports (other than 1000Base-X) do not support auto-negotiation and
therefore require the operator to enter the speed command with the desired
operating rate. The link partner must be similarly configured. SFP+/QSFP
fiber ports using fiber media do not support auto-negotiation, although it
must be enabled when using Direct Attach Copper cables if the link partner
also supports auto-negotiation. 1G SFP fiber ports should have auto-
negotiation enabled. SFP transceivers in an SFP+ port should have auto-