PROBLEM

You get this when trying to SSH to a host from some IP (Let's assume it's 111.22.33.44 for the scope of this problem):

ssh_exchange_identification: Connection closed by remote host

What to do?

SOLUTION

It had to do with security and /etc/hosts.allow in my case.  The steps are:

• vi /etc/hosts.allow (Or if you prefer nano /etc/hosts.allow OR pico /etc/hosts.allow)
• Add lines at the end such as:

# My Remote Host
sshd: 111.22.  

• Above are examples of IP octets.  We are using 111.22 if the remote IP is 111.22.33.44 and CIDR is 111.22.0.0/16)
• Save the file and exit (In VI use :wq! )
• Try again from the IP of the remote host (In the above case, 111.22.33.44 )

Or at least that was the source of the issue for me.  Hope it helps!

Good Luck!
TK