Try formatting it like this: ProxyCommand ssh jumpHost -W %h:%p -W is essentiall...

keeperofdakeys on Sept 7, 2015 | parent | context | favorite | on: Sshmuxd: SSH proxy to replace jump hosts

Try formatting it like this:

    ProxyCommand ssh jumpHost -W %h:%p

-W is essentially the same as using nc, however it doesn't require executing a command on the jumphost. This project uses that fact to make the jumphost more secure (you can't execute arbitrary commands), and do destination white-listing for each user.