Checking Sequence

Overview

Red Alert's checking sequence is designed to provide foolproof, end-to-end verification of your device's accessibility to the Internet. Every error condition is triple-checked using three fully independent Internet connections with no backbone networks, local Internet access providers, or local network equipment in common among them. You are not notified about a problem unless Red Alert has tried three different paths to your device and found it to be inaccessible or malfunctioning all three times.

IP Ranges of Red Alert Agents

The three network ranges used by Red Alert agents are:

  • 63.67.132.1/24
  • 205.163.212.1/24
  • 12.180.99.49/29

Details

Four times per hour, around the clock, Red Alert performs the following sequence of steps:

  1. Red Alert attempts to open a TCP connection to your device. If the attempt succeeds, this confirms that
    • the device is running,
    • the device's local network is functioning
    • the device has Internet connectivity, and
    • server software is accepting TCP connections from visitors via the Internet.
    But if the attempt fails, Red Alert enters a diagnostic mode to determine the device's error condition.
     
  2. If the device is a web server, then once the TCP connection is opened, Red Alert sends an HTTP request for the URL that you have provided. It examines the web page, file, or other response received, in order to check its contents for other error conditions.
     
  3. If an error condition has been detected, Red Alert starts over again at Step 1 above, this time using a second Internet connection that is fully independent of the first one. If this check also yields an error condition, then Red Alert again starts over at Step 1, using a third Internet connection.
     
  4. If all three checks have revealed an error condition, Red Alert sends notifications via email and pager to the people whom you have specified to be notified about this particular error condition for this device at this time of day. Red Alert may also collect more diagnostic information, such as traceroute results if you have activated the AutoTrace feature. All diagnostics are recorded in the device's error log along with a list of who was notified.