Nagios is a popular open source monitoring solution for network monitoring and application monitoring. With the iLert integration, you can be assured that all of your alerts are acted upon. You will never miss a critical alert and always alert the right person using iLert's on-call schedules, automatic escalation, and multiple alerting channels. When Nagios creates an alert, iLert will alert the on-call person through their preferred channel, including SMS, phone calls, push notifications and Slack. iLert will automatically escalate to the next person, if the alert is not acknowledged. iLert also lets you define alerting rules based on support hours and delay alerts until your support hours start.