training (40GE interface view)

Usage Scenario

With the increase of transmission rate or frequency, attenuation of signal's high-frequency components becomes increasingly severe. To guarantee transmission performance of signals, it is necessary to compensate for signals, and commonly used compensation technologies are pre-emphasis and balancing. The pre-emphasis technology increases high-frequency components of signals at the transmit end of transmission lines to compensate attenuation during the transmission. However, the pre-emphasis technology increases crosstalk while amplifying high-frequency components. To solve this problem, the balancing technology is developed. The balancing technology is used at the receive end of transmission lines to function like a filter for filtering high-frequency crosstalk.

After the training function is enabled on a 40GE interface, the transmit end exchanges frames with the receive end to automatically set the pre-emphasis and balancing parameters, improving processing efficiency of the two technologies. Note that the negotiated parameters for the training function are obtained based on the site environment. If the site environment changes, for example, from high-temperature environment to low-temperature environment, the parameters may be inaccurate. Therefore, bit errors may occur when the training function is enabled. The training function is optional in IEEE802.3 standards, and its implementation on different types of products from various vendors may differ.

When connecting two devices, enable or disable the training function on both ends simultaneously. By default, the training function is enabled on a 40GE interface. If the training function is disabled on the remote device or the remote device does not support the function, run the training disable or undo training enable command to disable the function.

Precautions

• The training disable and undo training enable commands can be configured on a 40GE interface only when the interface connects to a high-speed cable and is not a physical member interface in a stack.

• After a cable is installed on a 40GE interface without the training disable configuration, the training enable configuration is automatically generated on the interface.

• If no cable is installed on an interface, only the training enable and undo training disable commands can be configured on the interface.

• If the display this include-default command is run on an interface to view the training configuration after a cable is installed on the interface, the default training enable configuration is always displayed in the command output and does not change with the training configuration change.

• The training configuration on an interface takes effect only after a cable is installed on the interface. If the cable is replaced with an optical module, the training disable and training enable configurations will be automatically deleted from the interface.

• If a 40GE interface is configured as a physical member interface in a stack system, the training disable and training enable configurations will be automatically deleted from the interface.

• If a 40GE interface has been configured as a physical member interface in a stack system, the training function is disabled on the interface by default and cannot be enabled.

• If the training disable or undo training enable command is configured on a 40GE interface of the S6720S-26Q-EI-24S-AC or S6720S-26Q-EI-24S-DC after a cable is installed on the interface, and the interface is connected to a remote interface on which the training function is disabled or a remote interface that does not support the training function, the two interfaces may not go Up or go Up after a delay. Therefore, configure the training disable or undo training enable command only when the training function is disabled on the remote interface or the remote interface does not support the training function. In other scenarios, it is recommended that you do not disable the training function.
• If the training configuration does not exist on an interface of a switch running V200R008C00 or an earlier version, the training disable configuration is automatically generated on the interface after the system software is upgraded to a version later than V200R009C00. If the training configuration exists on the interface, the configuration remains unchanged after the system software is upgraded to a version later than V200R009C00.