ssh connection error. How to fix?

Question

SSH

When connecting via ssh to ubuntu on a virtual machine, an error occurs.
Linux alexandr-VirtualBox 4.4.0-24-generic #43-Ubuntu SMP Wed Jun 8 19:27:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Connecting to servers on the internet is fine.
Connecting via localhost to itself via ssh also works.
telnet seems to indicate that there is a connection.

How to fix connection error?

Answer 1

PuTTY needs to be updated to the latest version.

Answer 2

"protocol violation" - see connection protocol parameters on server and client.