Still Using an SMS Modem for Notifications?

How-to Articles
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When monitoring tools like Checkmk fail to transmit alerts due to internet or infrastructure issues, critical incidents can be missed.

For on-prem installations you want alerting to be independent from network, internet connection and infrastructure issues. An SMS modem with a SIM card might be a solution. However, it comes with some downsides:

  • Use of extra hardware
  • Can fail without recognition, especially if rarely used, e.g. running out of pre-paid credits, weak network coverage
  • SMS text is not alerting, e.g. just a beep, no escalation, just one channel, no acknowledgement or team collaboration, etc.

There are alternatives to using local SMS modems. Here are some ideas using a cloud bases alerting service.

1. Website Monitoring

Configure an external alerting tool to check a URL (e.g. the Checkmk URL) at regular intervals. If the URL is unreachable or errors occur, an alert is triggered. This monitors your tool’s availability and internet connectivity.

2. Heartbeat Monitor

Set up periodic HTTP requests (GET/POST) to a cloud-based alerting service. If requests stop arriving within a defined interval, the alerting tool raises an alert. You can use a cron job and curl or an actual check in Checkmk. Useful for verifying consistent internet or tool uptime.

3. Round-Trip Check

Combine website monitoring and heartbeat checks. A request (external or internal) triggers a backend response and as a result the heartbeat is sent to the alerting service. This round-trip helps to check additional end-to-end system functionality.

These options ensure you’re alerted even if Checkmk cannot connect to the internet. The above is extracted from an article about heartbeat and website check functionalities of the mobile alerting service SIGN4.

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Still the SMS-Eagle and the full control

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But in the end SMS is the only option if you have no real mobile internet connection.

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Thanks for your comments …

Certainly, if the facility has no internet connection at all, SMS is still a good option. Also, in general I agree that SMS is still fine for a variety of use cases - but it also lacks some functionalities when it comes to critical alerting.

Sometimes the good old SMS-to-email services of the carriers or service providers can help. In this case you can send the SMS text form Checkmk and use the resulting email to trigger a “real” alert using an alerting service.

If a facility usually has an internet connection and SMS text is just used as a backup, another idea is to use a mobile link as a backup just to be able to send critical alerts when the primary link is down.

In all these cases there still is a chance of no alert when the whole facility is down. That’s why I like the heartbeat option.

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Just throwing cross monitoring into the mix here: Have your Checkmk sites monitor each other (what exactly depends on your use-case) and leverage the fact, that by default Checkmk sites send notifications locally. This enables e.g., one location to monitor another location and if the latter location fails somehow, the other location can still notify. And vice versa.

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