Usage Scenario
On a large-scale Ethernet network, manually setting the interface rate and duplex mode, verifying the configurations of devices, and checking statistics about Ethernet interfaces require a great deal of time and human input. Therefore, it is recommended that manually setting the interface rate and duplex mode be adopted only when auto-negotiation of an Ethernet link fails or a problem occurs with auto-negotiation. When there is an auto-negotiation problem, you are recommended to upgrade software or hardware of the device to support the auto-negotiation standard defined in IEEE802.3u/z.
It is recommended that Ethernet interfaces work in auto-negotiation mode provided that the interfaces support this mode. Auto-negotiation is disabled only when two ends of a link work at unmatched rates or duplex modes. In this case, you need to manually set the interface rate and duplex mode.
- The duplex { half | full | auto } command can be used to change the duplex mode of an electrical Ethernet interface.
- The speed { 10 | 100 | 1000 | auto } command can be used to change the rate of an electrical Ethernet interface.
Two Ethernet electrical interfaces at both ends of a link can have different configurations of the auto-negotiation mode.
Two Ethernet optical interfaces at both ends of a link must both have auto-negotiation enabled or disabled. Enabling auto-negotiation on Ethernet optical interfaces is recommended.
Configuration Impact
If both ends support auto-negotiation, the duplex mode with a lower priority is adopted. Interconnected devices working in auto-negotiation mode is the prerequisite to the auto-negotiation mechanism. If one end works in auto-negotiation mode while the other end works in fixed mode, the auto-negotiation mechanism does not take effect.
Precautions
If a GE electrical interface works at 1000 Mbit/s, it can work only in full-duplex mode.
When the undo
negotiation auto command is run to cancel the autonegotiation configuration, a message is added to prompt users to ensure consistent configuration on the two ends.
If a GE electrical interface works at 1000 Mbit/s, it can work only in full-duplex mode.
The
negotiation auto command takes effect only in the GE interface view.
If the
negotiation auto command is run in the view of a GE interface that supports the GE, 25GE, and 10GE rates and the working mode of the interface is switched to 10GE or 25GE, the auto-negotiation configuration is reserved but does not take effect. After the working mode of the interface is switched back to GE, the auto-negotiation configuration is not lost either.
