What happens to calls when the 3CX server is rebooted?

When the 3CX server is rebooted, calls may indeed be lost unless they are managed properly. This is because a reboot of the server interrupts the connection handling, which can lead to active calls being disconnected during the process.

For ongoing calls, it's essential to have proper call management strategies in place—such as session border controllers or failover mechanisms—that can help mitigate the impact of a server reboot. However, if the server is simply restarted without these safeguards, users may experience call drops.

In contrast, the other options do not accurately reflect what occurs during a server reboot. For example, calls cannot be automatically redirected to a backup if one is not configured, and there's no guarantee that calls would remain unaffected during such an operation. Additionally, rebooting the server—whether planned or unplanned—results in similar disruptions, debunking the idea that only unplanned reboots would impact calls. Thus, understanding the management of calls during server maintenance is crucial in maintaining uninterrupted communication services.