The Eth-Trunk link of the M-LAG master device goes Down, and the dual-homing scenario changes to a single-homing scenario. If the M-LAG master device fails, the M-LAG backup device becomes the master device and continues to forward traffic, and its Eth-Trunk link is still in Up state. Traffic forwarding in case of a peer-link failure After the negotiation is complete, all interfaces except M-LAG member interfaces go Up and M-LAG member interfaces go Up 2 minutes later to ensure that the interface isolation mechanism takes effect. In this case, traffic is forwarded only by the M-LAG master device.Īfter the faulty peer-link recovers, peer-link interfaces go Up, and M-LAG member devices renegotiate with each other. Therefore, the M-LAG backup device sets all physical interfaces except the peer-link interface, stack interface, and management interface to Error-Down state.
LAG SWITCH APP MAC
If they forward traffic at the same time, a broadcast storm or MAC address flapping occurs. When the peer-link fails, the two M-LAG devices cannot forward traffic at the same time. If the local device receives DAD packets from the remote device, the local device considers that the peer-link fails. If the local device does not receive any DAD packet from the remote device within a specified period, the local device considers that the remote device fails. If an M-LAG member device detects that the peer-link is Down, it immediately initiates DAD through the DAD link. Traffic forwarding in case of an M-LAG member interface failure The single-homing scenario is restored to a dual-homing scenario, and traffic is forwarded in load balancing mode. When the M-LAG device where the faulty M-LAG member interface resides receives traffic sent from the network side to the user side (marked in yellow in the figure), the device forwards the traffic to the M-LAG device that works properly through the peer-link for forwarding to the user side.Īfter the faulty M-LAG member interface recovers and goes Up, MAC address entry synchronization is triggered in the M-LAG system. In this case, the interface isolation mechanism does not take effect. Because an M-LAG member interface fails, the dual-homing scenario changes to a single-homing scenario. The network-side device does not detect the fault and still sends traffic to the two M-LAG devices. When an M-LAG member interface fails, traffic sent from the user side to the network side (marked in green in the figure) is load balanced between normal links. Traffic forwarding in case of an uplink failure If the uplink fails, the M-LAG member interface is triggered to go Down, preventing traffic loss. To solve this problem, you can configure the link between management interfaces as the DAD link, or configure the Monitor Link function to associate the M-LAG member interface with the uplink interface. In this case, traffic sent from the user side to the M-LAG master device is discarded because no uplink interface is available. If the peer-link also fails, a dual-active conflict occurs in the M-LAG, and DAD cannot be performed. If the faulty link is the DAD link, the M-LAG continues to work properly without being affected. Otherwise, the uplink traffic that reaches the master device cannot reach the backup device through the peer-link. When a device is connected to a Layer 3 network through an M-LAG, a best-effort link must be configured between the M-LAG master and backup devices. If the uplink of the M-LAG master device fails, traffic passing through the M-LAG master device is forwarded by the M-LAG backup device through the peer-link. In the following figure, a device is connected to a common Ethernet network through an M-LAG.
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