Problem Description
A CE switch connects to an H3C switch through three cables, a link aggregation group (LAG) is created on each of them, and three connected interfaces are added to the LAG at each end. After the configuration is complete, two devices cannot communicate or learn the MAC address of each other.
Root Cause
Run the display interface eth-trunk command to check the LAG status. The status of each physical interface is Up but the Eth-Trunk status is Down, the protocol configuration on both devices may be inconsistent.
For a CE switch, link aggregation can work in manual load balancing mode or LACP mode. By default, link aggregation works in manual load balancing mode. That is, the LACP mode is disabled.
Check the configuration of both devices. The H3C switch uses the dynamic aggregation mode. In this mode, all member interfaces in the group are enabled with LACP. The CE switch uses the manual load balancing mode by default. That is, LACP is disabled. The preceding problem is caused by the incorrect protocol configuration of two devices.
Procedure
Run the mode lacp-static command in the Eth-Trunk interface view of the CE switch to change the link aggregation mode to static LACP.
