$ cat .ssh/config
Host ssh-proxy
Hostname ssh-proxy.domain.net
DynamicForward 9999
Host ssh-host-with-proxy
Hostname host.domain.com
ProxyCommand nc -x localhost:9999 %h %p
$ ssh ssh-proxy
[ ... ]
<new terminal>
$ ssh ssh-host-with-proxy
[ ... ]
# Alternative with SSH in Background
$ ssh -f -N ssh-proxy
[ ... ]
<same terminal>
$ ssh ssh-host-with-proxy
[ ... ]