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RobLang-3803 asked ·

How do I log HTTP 525 errors in IIS?

I have Windows Server 2016 Datacenter (1607) running on AWS EC2 serving .NET Framework 4.7.2 application on IIS (10.0.14393.0). We use Cloudflare as a proxy (DDoS protection). Cloudflare tells us that IIS intermittently returns HTTP 525 when negotiating SSL.

Cloudflare insist that the problem is at the server and not with them.

AWS did not have outages and I have other services on the server that were running correctly at the time. The certificates are with LetsEncrypt and are valid at the time (the service that renews and updates runs at a different time to the errors occuring). Server is patched up to date.

There are no IIS logs at time of the errors. How do I log 525 errors either in IIS or via Windows Event Viewer?

Many thanks in advance.

windows-server-2016
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MotoX80 answered ·
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Failed request tracing is what I was looking for.

It was not installed on the server by default, you need to add Program Features -> Server Role -> IIS -> Health and Diagnostics -> Failed Request Tracing.

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