Use "ProxyCommand" in your ~/.ssh/config to easily access servers hidden behind port knocking and jump hosts. Also check out the .

Use Gateway/Jumphost

Host unreachable_host
  ProxyCommand ssh gateway_host exec nc %h %p

Automatic Jump Host Proxying

Host «your jump host>
  ForwardAgent yes
  Hostname «your jump host>
  User «your user name on jump host>

# Note the server list can have wild cards, e.g. "webserver-* database*"
Host «server list>
  ForwardAgent yes
  User «your user name on all these hosts>
  ProxyCommand ssh -q «your jump host> nc -q0 %h 22

Automatic Port Knocking

Host myserver
   User myuser
   Host myserver.com
   ProxyCommand bash -c '/usr/bin/knock %h 1000 2000 3000 4000; sleep 1; exec /bin/nc %h %p'