Check and config supported SSH protocol version.
Method One
If you want to check what SSH protocol version are supported by a local OpenSSH server, you can refer to /etc/ssh/sshd_config file. Open /etc/ssh/sshd_config with a vi editor and look for "Protocol" field. You can also config the version over this parameter. If you change the paarameter so you should restart sshd.
If it shows the following, it means that OpenSSH server supports SSH2 only.
Protocol 2
If it displays the following instead, OpenSSH server supports both SSH1 and SSH2.
Protocol 1,2
Method Two
If you cannot access /etc/ssh/sshd_config because OpenSSH server is running on a remote server, you can test its SSH protocol support by using SSH client program called ssh. More specifically, we force ssh to use a specific SSH protocol, and see how the remote SSH server responds.
The following command will force ssh command to use SSH1
# ssh -1 user@remote_server
If the remote SSH server supports SSH2 only, the first command with "-1" option will fails with an error message like this:
# ssh -2 user@remote_server
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