IIS/ Windows 服务器 2019 无 HTTP/2

Question

I have a server installed with Windows Server 2019 and IIS 10. According to https://learn.microsoft.com/en-us/iis/get-started/whats-new-in-iis-10/http2-on-iis all https sites should work using HTTP/2 out of the box.

However my site works in http/1.1 mode only. I checked with Chrome/Firefox and online tools like https://tools.keycdn.com/http2-test and the result is "HTTP/2 protocol is not supported. ALPN extension is not supported."

I checked the common reasons for http/1.1 fallback:

• Windows authentication - this is disabled for my site
• clear text - https is enabled on my site with a valid SSL certificate
• Bandwidth throttling - not enabled on my site
• registry settings for disabling HTTP/2 - not set

My web site uses ASP.NET, but simple html is also downloaded in HTTP/1.1.

Any idea what to examine next?

Answer 1

This is probably the answer you're all looking for:

Open your registry editor and navigate to:

Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\HTTP\Parameters

Make sure you have the following entries:

EnableHttp2Cleartext REG_DWORD    1
EnableHttp2Tls    REG_DWORD    1

Reboot.

Answer 2

In my case I disabled TLS 1.0 and TLS 1.1 For this you have two options:

1. Edit the registry keys
2. Install IISCrypto and uncheck TLS 1.0 and TLS 1.1

Note: You need to reboot the server in order to apply the changes