SSH config

  • define the following section in your /home/guest/.ssh/config (note the indentation!)
Host lxplus
   User %USERNAME%
   Compression yes
   Protocol 2
   ForwardAgent yes
   ForwardX11 yes
   ForwardX11Trusted no
   LocalForward 9999
   LocalForward 9998
   DynamicForward 1080
  • for each machine inside you would like to reach within the CERN network (and is not directly accessible from outside) add the following entry:
Host pcfaserdcsdev
    ForwardAgent yes
    ForwardX11 yes
    ForwardX11Trusted no
    ProxyCommand ssh lxplus nc %h 22
  • now you can directly ssh to the corresponding host without explicitly hopping via lxplus. You might still need to enter your password twice.

automatic SOCKS5 tunnel to CERN

  • create a pac file in your home directory (/home/guest/.proxy.pac) with the following content:
function FindProxyForURL(url, host) {
   var proxy_socks_cern = "SOCKS5";
   var proxy_no = "DIRECT";

   if (dnsDomainIs(host, "")) {
      return proxy_socks_cern;
  //if nothing else, take the default way into the internet!
  return no_proxy;
  • adjust the Firefox settings in order to use that file: Preferences > General > Network Settings (at the very bottom) > Settings
  • select "Automatic proxy configuration URL" and specify the path to the proxy file from above, e.g. file:///home/guest/.proxy.pac (note: you need file:// in the beginning)
  • open a SSH connection to lxplus
  • as long as your SSH connection to lxplus is open, all traffic to will be sent through the SSH tunnel and can reach resources restricted to the internal CERN network
  • more targets inside the CERN network can be added easily to the pac file, by just duplicating the if section with a different URL
  • in order to make Firefox aware of a changed pac file, one needs to reload the file in the Network Setting dialog

Windows remote desktop connection

  • make sure your target machine is listed under the lxplus Host section in the ssh config
  • open a ssh connection to lxplus
  • locally run the rdesktop comand with the correct port:
rdesktop -d CERN localhost:9999

VNC connection

  • login to the machine which you want to reach via VNC and start a server instance:
vncserver -localhost -name $HOSTNAME-vnc -geometry 1920x1080
  • from your local machine, run the vnc viewer, where you have to replace :1 by the actual session number you got when you started the server in the previous step:
vncviewer -via :1

X2go connection

-- BenediktVormwald - 2020-06-19
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Topic revision: r2 - 2020-06-26 - BenediktVormwald
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