520 Errors for Telstra Customers in Australia on SIN COLO

Hi All!

Our staff/customers are intermittently seeing 520 Unknown Errors from Cloudflare when using Telstra fixed line connections in Australia, when those requests are routed through the SIN COLO. We don’t see these errors with other providers, such as Aussie Broadband, just Telstra, at this stage.

I noted that Aussie Broadband seems to always route through SYD COLO, whereas Telstra is always routing through SIN COLO.

I’ve checked the web server and the requests are resolving just fine, status 200, quickly, no problems at the server end. Not seeing anything in the error log. The server is sitting in Sydney in AWS EC2, not overloaded, plenty of bandwidth, so just trying to eliminate network issues here. I just can’t find an error at the server end at all.

Is anyone else seeing anything similar or have any suggestions at all? I’ve hit a dead end on troubleshooting and suspect it might be a network/routing issues between Cloudflare SIN and AWS SYD.

For anyone internal to CF that may see this the details of the request are below:

Ray ID: 688a7d0318e33c64
Time: 2021-09-02 23:23:50 UTC

SIN is actually Singapore, while Hong Kong is using HKG :wink:


Corrected. Thanks! It’s definitely between CF SIN and AWS SYD here.

Hi @lcl,

Due to the number of 520s being reported in similar circumstances, we are escalating the issue to Cloudflare Support. The original incident should have been resolved and your issue may well be unrelated.

We recommend checking these troubleshooting tips, if you haven’t already.

If you have been through these thoroughly and are not seeing corresponding issues on your network/server and you have a ticket number with Cloudflare, please reply and post that #.

To enable efficient troubleshooting by support, please ensure you include the following on the ticket:

  • example URL(s) where you are seeing the error
  • Ray IDs from the 520 pages
  • output from a traceroute from any impacted user
  • output of example.com/cdn-cgi/trace - replace example.com with the affected domain.
  • Also include two HAR file(s) : one detailing your request with Cloudflare enabled on your website and the other with Cloudflare temporarily disabled - see How do I temporarily deactivate Cloudflare ?
1 Like

So as part of https://community.cloudflare.com/t/random-520-errors/ we fixed an issue with origins silently ending a keepalive connection that was causing very rare 520 errors.

Thus we recommend testing again - if you still see 520s - make sure you follow the guidance in our community tip here:

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