set ethernet speed down-grade
Function
The set ethernet speed down-grade command enables the rate decrease auto-negotiation function on an interface.
The undo set ethernet speed down-grade command disables the rate decrease auto-negotiation function on an interface.
By default, rate decrease auto-negotiation is disabled on an interface.
Rate decrease auto-negotiation takes effect only on MultiGE interfaces, GE optical interfaces that have GE copper modules installed or GE electrical interfaces, the last four 10GE electrical interfaces on the ES5D21X08T00 card of the S5730-HI, S5731-H, and S5731S-H.
The last four GE interfaces (based on the interface number) on the S5720-PC-EI and S5720-P-EI do not support rate decrease auto-negotiation.
Usage Guidelines
Usage Scenario
Two devices are connected through two GE electrical interfaces using a network cable. The two GE interfaces are configured to work in rate auto-negotiation mode. The network cable can only work at the rate of 100 Mbit/s or 10 Mbit/s because it deteriorates, but the maximum rate supported by the two GE interfaces is 1000 Mbit/s. The interfaces negotiate the working rate to 1000 Mbit/s, but cannot go Up because the network cable does not support the rate of 1000 Mbit/s.
You can use the rate decrease auto-negotiation function to solve this problem. After rate decrease auto-negotiation is enabled using this command, the two GE interfaces can decrease the negotiated rate to 10 Mbit/s or 100 Mbit/s, and then can go Up.
Prerequisites
The two connected interfaces work in auto-negotiation mode. If an interface works in non-auto-negotiation mode, run the negotiation auto command in the interface view to configure it to work in auto-negotiation mode.
Precautions
If rate decrease auto-negotiation is configured on the local interface, but not on the remote interface, the local interface can still decrease the negotiated rate to 100 Mbit/s. If the rate decrease auto-negotiation function is configured on an interface of the S5720-28X-PWH-LI-AC, S5720-28X-PWH-LI-ACF, S6720-32C-SI-AC, S6720-32C-SI-DC, S6720-32C-PWH-SI-AC, S6720-32C-PWH-SI, S6720-52X-PWH-SI, S6720-56C-PWH-SI-AC or S6720-56C-PWH-SI, you must also configure this function on the remote interface; otherwise, the local and remote interfaces may not go Up.
If the network cable quality is low, a MultiGE interface takes longer time to go Up after the rate decrease auto-negotiation function is configured. For example, if the rate is decreased from 10 Gbit/s to 100 Mbit/s, the MultiGE interface takes about 40 seconds to go Up. If the rate is decreased from 2.5 Gbit/s to 100 Mbit/s, the MultiGE interface takes about 20 seconds to go Up. It is recommended that you replace the network cable.
After the rate decrease auto-negotiation function is configured on a MultiGE interface of the S5720-28X-PWH-LI-AC, S5720-28X-PWH-LI-ACF and a network cable is removed and reinstalled on the interface in Down state continuously, the interface rate automatically decreases to 1000 Mbit/s. You can remove and reinstall the network cable again after the interface goes Up or run the shutdown and undo shutdown commands on the remote interface to restore the interface rate to 2500 Mbit/s.