I manage a small business network using pfSense and want a simple way to monitor a few internal servers by ping or TCP port, then send notifications when they become unreachable. External uptime monitoring already watches the firewall, but the servers use private addresses behind it, so an outside service cannot check them directly. I considered using pfSense's gateway monitoring or running something lightweight such as Zabbix or Uptime Kuma on a Raspberry Pi, but that raises the question of who monitors the monitoring system if the firewall, power, or site goes down. Ideally, the solution would use very little power and run reliably on a UPS.
5 Answers
A dead-man’s-switch approach works well here. Have the Raspberry Pi send a scheduled check-in to an external service such as Healthchecks.io. The Pi can monitor the internal hosts locally, and the outside service alerts you when check-ins stop, whether the cause is a server failure, power loss, or the firewall going down.
The cleanest design is to split the monitoring into two layers: an internal monitor checks the private servers, while an external service monitors a heartbeat from the internal system. If the heartbeat stops, the external service alerts you. That covers both a failed server and a complete site or firewall outage.
LibreNMS can handle basic ping-only monitoring, although it may be more than you need if all you want is reachability checks. Uptime Kuma is usually simpler to deploy for a small number of devices.
A small cloud function can periodically test the firewall or a published service and send email or SMS alerts when it stops responding. It costs very little, but it will not replace an internal monitor for servers that are only reachable through private addresses.
Uptime Kuma is a good fit for this. Run it on a small Raspberry Pi or another low-power device and configure ping or TCP checks for the internal servers. For site-wide outages, pair it with an external heartbeat or uptime service so you still get an alert if the Pi and pfSense go offline.
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