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How LoadMaster High Availability works

On LoadMaster High Availability(HA) is achieved by a hot-standby, failover mechanism. Two identical LoadMaster units are integrated into the network as a cluster. One machine serves as the active LoadMaster and the second one remains in a standby, idle state - always prepared to take over the activities from the active server. This cluster appears as a single logical unit to the internet side and to the server farm side connections.



With a HA cluster, each network interface has an individual IP address and one shared IP address which is shared with the partner unit. The shared IP address is identical for both LoadMaster appliances, though it is associated with only the active LoadMaster at any given time.


LoadMaster uses CARP at  the HA protocol. Each HA unit provides health status updates to the other partner via CARP and the health status updates are used by the standby LoadMaster to decide when it is appropriate to assume the active role. As long as the Active Unit is sending CARP updates the standby unit will remain in standby mode. For CARP to work between a pair of LoadMasters, both LoadMasters must be on the same broadcast domain.


If the standby unit stops receiving CARP Messages it will assume Active Role ensuring traffic is maintained.



For more information see