Dell N3200-ON Networking N-Series Switches CLI Reference Guide version 6.8.0 - Page 463

Use the auto parameter to enable auto-negotiation on an interface. Autonegotiation on copper interfaces selects a clock primary, 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 autonegotiation 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 primary 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 autonegotiation enabled. SFP transceivers in an SFP+ port should have autonegotiation enabled. The default behavior is to enable auto-negotiation when an SFP transceiver is inserted into an SFP+ port, unless a fixed speed is configured. Likewise, SFP+ ports connected via copper Direct Attach Cables must have auto-negotiation enabled if the link partner is also capable of performing auto-negotiation. If the link partner cannot perform auto-negotiation, then a fixed speed must be utilized. In all cases, the link partners need compatible settings, e.g., both sides must be set to use auto-negotiation or a fixed speed. In the case of a fixed speed link, both sides must be set to the same speed. Layer 2 Switching Commands 463