Why does traffic forwarding fail when the switch is connected to another device through an Eth-Trunk

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After an Eth-Trunk is configured on the switch, the manual load balancing mode is adopted on the Eth-Trunk by default. If the device connected to the switch uses the static LACP mode after link aggregation is configured, the two devices use different working modes at two ends of the Eth-Trunk. As a result, traffic cannot be transmitted on the Eth-Trunk. To ensure traffic transmission on the Eth-Trunk, you need to set the same working mode on the two devices.

Other related questions:
Why does traffic forwarding fail when an S series switch is connected to another device through Eth-Trunk
After Eth-Trunk link aggregation is configured for an S series switch (except the S1700), the Eth-Trunk works in manual load balancing mode by default. If Eth-Trunk link aggregation is also configured for the peer device, the Eth-Trunk works in LACP mode by default. The two ends of the Eth-Trunk work in different default modes, resulting in forward traffic failure. To ensure normal traffic forwarding, you must configure the same working mode for the two ends.

Traffic is not forwarded through all member interfaces of an Eth-Trunk in a stack. Why
When a stack device forwards traffic, an Eth-Trunk may select a member interface of another stack device through the hash algorithm, which occupies bandwidth resources between stack devices and reduces the traffic forwarding efficiency. To address the preceding problem, run the local-preference enable command to enable the Eth-Trunk to preferentially forward local traffic. That is, traffic arriving at the local device is preferentially forwarded through member interfaces of the local device. If the local device has no member interface, the member interface of another stack device is used to forward traffic. This saves bandwidth resources between stack devices and improves the traffic forwarding efficiency. By default, an Eth-Trunk is enabled to preferentially forward local traffic. Before configuring an Eth-Trunk to preferentially forward local traffic, ensure that the outbound bandwidth of Eth-Trunk member interfaces is sufficient for forwarding local traffic. If the outbound interface bandwidth is insufficient, some packets are dropped.

How is the LACP mode configured when a CE switch connects to a third-party device through an Eth-Trunk
Run the mode { lacp-static | lacp-dynamic | manual [ load-balance ] } command in the Eth-Trunk interface view to configure the LACP mode of the Eth-Trunk on the CE switch. When a CE switch connects to a third-party device, the LACP modes must be consistent on the two ends. Mainstream network devices that connect to CE switches include devices from Cisco, Juniper, and H3C. The table on the right describes the mapping between aggregation modes.

How can I configure an Eth-Trunk on CE switches to preferentially forward local traffic
Run the undo local-preference disable command in the Eth-Trunk interface view to enable preferential local traffic forwarding on the Eth-Trunk.

<HUAWEI> system-view
[~HUAWEI] interface eth-trunk 10
[*HUAWEI-Eth-Trunk10] undo local-preference disable
[*HUAWEI-Eth-Trunk10] commit

Whether the function that preferentially forwards local traffic on an Eth-Trunk is enabled by default on CE switches
The local traffic preferential forwarding function on an Eth-Trunk is enabled by default. To disable local traffic preferential forwarding, run the local-preference disable command in the Eth-Trunk interface view.

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