Issue with multiple VM alert rule not sending all SMS alerts

Question

Hello,

I have set up the default alert rules for multiple VMs, but I'm having trouble receiving all SMS alerts when multiple VMs trigger the rule. Specifically, I receive 1 SMS message when one of the VMs goes down, but if all 4 VMs go down, I'm only receiving 1-3 SMS messages instead of all 4. However, I do receive all 4 VM alerts via email. I'm wondering if there's a setting that might be limiting or deduplicating the SMS alerts or if the issue is caused by using 1 alert rule for multiple VMs.

Can anyone help? Thank you.

Answer 1

You can check the following limits for Azure Monitor SMS Delivery. Azure Monitor might throttle SMS alerts to prevent excessive charges. Check your Action Group configuration for any notification throttling limits set for SMS.

https://learn.microsoft.com/en-us/azure/azure-monitor/service-limits

Action Groups have "Dedupe" and "Coalesce" settings for notifications. Dedupe combines similar alerts into one message, while Coalesce groups multiple alerts within a timeframe.

for more information

https://learn.microsoft.com/en-us/azure/defender-for-cloud/configure-email-notifications