Reusing a shared master ssh connection across many ssh client instances (really fast login after first login).

.ssh_config

Host my-server                                    # Alias for this server so you can run "$ ssh my-server"
	#ForwardAgent yes                         # Use local agent to password-free authentication
	#User my_user                             # Name of remote user
	#IdentityFile ~/.ssh/id_rsa-${MY_SERVER}  # I suggest you to use key-pair auth
	Hostname my.server.fqdn                   # Real server hostname
	ControlMaster auto                        # share a single ssh connection across many ssh instances
	ControlPersist 60                         # send master connection to background, close it if idle for 60 seconds
	ControlPath ~/.ssh/master/ssh-%h          # place local sharing socket in a secure place