ssh ProxyCommand : Connect to a Host through an other

With ssh you can jump host using ProxyCommand. Some times you can only access a remote server via ssh by first login into an intermediary server (or firewall/jump host). So you first login into to the intermediary server and then ssh to another server.

Once you’ve opened a firewall session (see : external ssh access), you can connect to sismo’s host.
With usual way, you have to use two ssh connection.
With ssh ProxyCommand you can connect directly to a remote host.

Usual connection process to you host

Connection way with ssh ProxyCommand

For that you just have to add the followings line to your ~/.ssh/config file.

Using ssh ProxyJump : -J

La version 7.3 d’OpenSSH offre une nouvelle option ’-J’ qui permet de spécifier un pivot lors d’une connexion.
La configuration précédente peut alors s’écrire.

ssh −J <login>@<machine.ssh.pivot><login_sur_machine_cible>@<machine.cible>

Dans notre cas à l’IPGP la commande sera donc :

$ ssh -J <login-sismologie>@ <machine.cible>

Others usefull doc

See ssh-keys documentation.
other ssh proxy command