Protocol major versions differ: 1 vs. 2. 

The error above normally comes up when you try to ssh into a machine which has it’s allowed ssh protocol versions locked down to a single version, today it’s normally version 2.

In the /etc/ssh/sshd_config file there’s a “Protocol” parameter which governs the allowed protocol version. It’s normally set to “2” for better security today.

Old days;

#Protocol 2,1


#Protocol 2

The ssh command allows you to specify a protocol version to use when establishing a connection.

To ssh using protocol version 1;

ssh -1 [ hostname]

[[email protected] ~]# ssh -1 abubu

Ro ssh using protocol version 2;

ssh -2 [ hostname]

[[email protected] ~]# ssh -2 abubu