SSH Tunnel / Bastion Hop config example

config.ssh

Host *
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/id_rsa

# Helps prevent timeout of connections due to inactivity
ServerAliveInterval 30
TCPKeepAlive yes

# Use key forwarding so I don't have to put my private key on the servers
ForwardAgent yes

Host bastion
	Hostname bastion.example.com
	User ec2-user
	IdentityFile ~/.ssh/id_rsa
	ProxyCommand none
	ForwardAgent yes
  
Host instance1
	Hostname instance1.vpc.internal
	User ec2-user
	IdentityFile ~/.ssh/id_rsa
	ProxyCommand ssh bastion -W %h:%p