多段SSH、ssh/config

ssh_config

Host step_server
  User          username
  Hostname      xx.xx.xx.xx (Step Server's IP)
  PreferredAuthentications publickey
  IdentityFile  ~/.ssh/private.key
  Port          22
 
### ssh -Wオプションの場合(最近はこっちのほうがオススメらしい)
Host server_in_private
  User     username
  Hostname xx.xx.xx.xx (Private IP)
  Port     22
  ProxyCommand ssh -W %h:%p step_server
 
### netcatの場合
Host server_in_private
  User     username
  Hostname xx.xx.xx.xx (Private IP)
  Port     22
  ProxyCommand ssh step_server nc -w 3600 %h %p (-wでtimeout時間を設定すること)