Disable TLS 1.2 stops RST packets

Environment,

Web server - Server 2012 R2, IIS 8, ASP.NET application

Firewall Cisco 5515

Un-Managed HP switches, No vlaning

Client has been using Curl from the outside to hit our application.

No one else should be using the server.

Using wireshark i can see, If I have TLS 1.2 enabled, every time they hit the server at the end there is a RST

If i disable TLS 1.2 there is no packet RST and everything looks fine.

What could be causing this?

Please let me know if you need anymore info.

Solution 1:

Are you 100% sure he is not testing with a higher or lower version of TLS, packet resets normally are attributed to the application not knowing what to do with it.