How does the internet availability check work?

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The preferred way of checking for internet availability is a UDP based traceroute to the following IP addresses in a random manner:

* 198.41.0.4
* 192.33.4.12
* 128.8.10.90
* 192.5.5.241
* 192.36.148.17
* 192.58.128.30
* 193.0.14.129
* 198.32.64.12
* 202.12.27.33

If any of the IP addresses are reached, the check is successful. However, if none of these IPs can be reached via traceroute, the node will try an HTTP based "ping" to all of the following URLs:

* google.com
* yahoo.com
* alltheweb.com

If any of the URLs are reached, the check is successful. If that also fails, the node will try to download a page from checkin.cloudtrax.com as a last resort.

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Comments

  • Avatar
    Peter Distol

    Could you describe the process in more detail?
    What is the traceroute success criteria - a complete trace without timeouts?
    Does the process try to traceroute all the specified IPs before moving to next stage of check (HTTP "ping") or just one random IP?

  • Avatar
    Ryan Detwiller

    Hi Peter - I updated the article above to clarify.

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