# File Transfer between Neumann and Max-Planck's Mechthild

## Problem

Network to Workstations is usually not full speed. So a file transfer over a middle-man computer is slower than directly transfering files between Neumann and Mechhild (Max-Planck-Institut).

Using scp or rsync is the way to go. However, Mechhild is behind a Gateway. So direct connection is not possible. Moreover, Neumann is not visible from Mechthild, because there is also a Gateway for the university's network.

## Solution

In short: open a SSH tunnel which is to be used with scp.

To create a tunnel with a machine inside the university network to a remote machine (such as Mechthild), you always have to call out, meaning the SSH tunnel has to opened up from inside the university network.
Therefore:

1. Open a Terminal on Neumann, or similar
2. Run the following command to open a ssh tunnel on the port 11223
ssh -L 11223:mechthild:22 <mpi-username>@linssh.mpi-magdeburg.mpg.de

Replace <mpi-username> with your credential. The port 11223 will be opened on Neumann. The value 11223 is arbitrary and should be currently unused.

3. On Neumann you can run a scp command in the following way to copy something from:
• Mechthild ⇒ Neumann:
scp -P 11223 <mpi-username>@localhost:/path/on/mechthild /path/on/Neumann
• Neumann ⇒ Mechthild:
scp -P 11223 /path/on/Neumann <user_at_mechthild>@localhost:/path/on/mechthild