Overview MAD

When the VSL channel in the stacking system fails, the stacking system is split to multiple virtual switching domains and there are multiple virtual switching control devices with the same global configuration (called control device for short). This is called multi-active. The global configuration of the split logical device is the same as that of the previous logical device, so there is network configuration conflict, resulting in the traffic abnormality. To avoid the influence for the services, MAD (Multi-Active Detection) emerges.

The current stacking system supports two MAD modes: MAD LACP, and MAD Fast-Hello, meeting different networking requirements.

The MAD status includes two kinds: Active and Recovery. Active indicates the normal working state and Recovery indicates the disabling state. In the Recovery state, all L2/L3 Ethernet interfaces and VLAN interfaces except for the VSL member ports and reserved ports are disabled by MAD.

When the device receives the MAD detection packets, compare the data in the packet with the data of the local logical device. If the VS Domain ID in the packet (virtual switching domain number of the sending end) is the same as that of the local logical device, and the Master ID in the packet (the member number of the control device in the virtual switching domain of the sending end) is different from the local logical device, it is regarded that multi-active happens and start the multi-active election. According to some election rules, in one virtual switching domain, just reserve one logical device to keep Active and the other logical devices enter the Recovery state.

During the MAD LACP networking, use the intermediate device; during the MAD Fast-Hello networking, you can use the intermediate device and also can adopt the direct-connection. If adopting the direct-connection mode, you need to ensure that there is the direct-connection line between any two virtual switching member devices for the MAD, that is, it is necessary to ensure the full connection.