How do I configure M-LAG and obtain information about M-LAG configuration restrictions and examples?


Multichassis Link Aggregation Group (M-LAG) implements link aggregation among multiple devices. One device is connected to two devices through M-LAG to constitute a dual-active system. M-LAG achieves device-level link reliability but not card-level link reliability.
For details about how to configure M-LAG, M-LAG configuration restrictions and configuration examples, see M-LAG Best Practices. This document also recommends M-LAG deployment models and configuration suggestions in more multi-feature scenarios.

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Traffic is not passing through ETH trunk in LAG configuration?
STP is enabled by default, check the ports status to see if they are blocked.

For M-LAG networking of CE series switches, how to prevent some ports on a slave switch from entering the Error-Down state upon peer-link failures
If M-LAG is used on an Ethernet, VXLAN, or IP network where a CE switch is dual-homed to two PEs, when the peer-link is faulty but the heartbeat status is normal, all interfaces except the management interface, peer-link interface, and stack interface on the slave device enter the Error-Down state. When the peer-link recovers, the M-LAG member interfaces in Error-Down state are restored to the Up state after 2 minutes by default. Other physical interfaces in Error-Down state are restored to the Up state automatically. In actual networking, however, some uplink interfaces that run routing protocols or are used as DAD heartbeat interfaces do not need to enter the Error-Down state when the peer-link is faulty. You can configure the function on non-M-LAG member interfaces. # Configure Eth-Trunk 2 on the slave switch to automatically enter the Error-Down state. system-view [~HUAWEI] interface eth-trunk 2 [*HUAWEI-Eth-Trunk2] m-lag unpaired-port suspend [*HUAWEI-Eth-Trunk2] commit - When the peer-link is faulty but the heartbeat status is normal, M-LAG member interfaces and only the interfaces having the m-lag unpaired-port suspend command configured enter the Error-Down state. - M-LAG member interfaces do not support the m-lag unpaired-port suspend command, so you are advised to configure them on both master and slave switches.

When a server is dual-homed to CE switches through M-LAG, the server cannot transmit traffic to one of the CE switches
The cause is that the LACP M-LAG system priorities and IDs of two CEs in the M-LAG are inconsistent. Eth-Trunks on both switches configured with M-LAG must use the same LACP M-LAG system priority and ID. - In V100R006C00 and earlier versions, run the lacp m-lag priority priority command on the Eth-Trunks of both switches configured with M-LAG to set the same LACP M-LAG system priority and run the lacp m-lag system-id mac-address command to set the same LACP M-LAG system ID. - In V200R001C00 and later versions, the slave switch in the M-LAG automatically synchronizes the LACP M-LAG system priority and ID of the master switch through the peer-link.

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