MOGON is only accessible via SSH with a special jump host named hpcgate.zdv.uni-mainz.de.

If you only need to do this occasionally, you can use this command:

ssh -J <username>@hpcgate.zdv.uni-mainz.de <username>@<service-node>

Simply replace <username> with your ZDV-username and <service-node> with the MOGON service-node you want to access. You can find an overview of the MOGON service nodes here.

You can also explicitly specify the SSH-Key for the connection:

ssh -i ~/Path/To/Private/Key -J <username>@hpcgate.zdv.uni-mainz.de -i ~/Path/To/Private/Key <username>@<service-node>

The SSH-Key for the jump host and the MOGON service node need not necessarily be identical. However, the SSH-Keys must have been added to your ZDV account and have the correct properties.

The ProxyJump option was added in OpenSSH 7.3 and is basically shorthand for the ProxyCommand. For OpenSSH versions less than 7.3. you can use the following command:

ssh -o ProxyCommand="ssh -W %h:%p <username>@hpcgate.zdv.uni-mainz.de" <username>@<service-node>

Simply replace <username> with your ZDV-username and <service-node> with the MOGON service-node you want to access. You can find an overview of the MOGON service nodes here.

If you need to login from the outside more often, you can configure your SSH client to perform these steps "automagically":

First edit your local ssh config (~/.ssh/config) and add the following lines, where the setting ForwardX11 yes is optional:

# MOGON jump host
Host hpcgate
    HostName hpcgate.zdv.uni-mainz.de
    User <username>
    IdentityFile ~/Path/To/Private/Key
 
# for access to MOGON I:
Host mogon 
    HostName mogon
    User <username>
    ProxyJump hpcgate
    ForwardX11 yes
    IdentityFile ~/Path/To/Private/Key
 
# for access to MOGON II:
Host mogon2
    HostName miil01
    User <username>
    ProxyJump hpcgate
    ForwardX11 yes
    IdentityFile ~/Path/To/Private/Key

For example, you can now simply use:

ssh mogon2

for access to a service node on MOGON I or II. (More information on the jumphost technique with ProxyCommand)

# MOGON jump host
Host hpcgate
    HostName hpcgate.zdv.uni-mainz.de
    User <username>
    IdentityFile ~/Path/To/Private/Key
 
# for access to MOGON I:
Host mogon 
    HostName mogon
    User <username>
    ForwardX11 yes
    IdentityFile ~/Path/To/Private/Key
    ProxyCommand ssh -W %h:%p hpcgate
 
# for access to MOGON II:
Host mogon2
    HostName miil01
    User <username>
    ForwardX11 yes
    IdentityFile ~/Path/To/Private/Key
    ProxyCommand ssh -W %h:%p hpcgate

For example, you can now simply use:

ssh mogon