The system failover is switching to a passive system when an active system is in a state of failure(e.g. hardware fault, network problem).
A passive system synchronizes all data from the master database in which is running in an active system by the Database Replication[1] and monitors the active system.
A passive system sends a heartbeat about every 10 seconds to an active system. If the passive does not receive a response from an active system for the Deadtime, the passive system switches the mode to "active".
This system failover enables continuous service and you can connect the management page without changing the URI because a virtual IP is automatically configured in a active system by the failover service.
The failover service in an active system listens to a heartbeat from a passive system on UDP port 6010.
All services in the active and passive devices work as shown in the table below.
| Service | Active System | Passive System |
|---|---|---|
| dhcpv4 | running | running |
| dhcpv6 | running | running |
| radius | running | running |
| logexp | running | running but only saves its Syslog. |
| failover | Configuring a Virtual IP | Monitoring a active system and replicating the database |
| Database | Master | Slave |
Note that, If an active system is recovered from a fault after another system has switched to the active mode, the recovered system switches to passive mode. In other words, The failback[2] does not occur.
You can configure the System Failover via the CLI.