4

I have the following configuration and want to establish a tunnel on a tunnel. I read already the following topic: How to put a tunnel in a tunnel?

My configuration:

Notebook --> Linux Server A --> Linux Server B

Notebook: Windows XP with putty
Linux Server A and B: Ubuntu 10.10

I have a ssh connection with a tunnel from my notebook via putty to Server A. Now I want to establish a tunnel from Server A to B, so that I can connect with an IDE directly to my jboss on Server B.

This is the command I tried on Server A to establish a tunnel:

ssh -t -L 8080:localhost:8080 Server B -p 8822

This won't work.

Anybody an idea how to establish a working tunnel?

6

What you're looking for is called "ssh multi-hop". It is quite possible to do this transparently, using the ProxyCommand directive in .ssh/config (or an equivalent config option in PuTTY, or what-have-you):

Host linux-server-b
  ProxyCommand ssh -q linux-server-a nc -q0 linux-server-b 22

What this does, when you try to connect to linux-server-b:

  • opens a SSH connection to linux-server-a
  • runs netcat there, and opens a TCP connection to linux-server-b
  • forwards this connection back to you

This way, you can use all the features of SSH, as if you were connected to linux-server-b directly; you can even chain multiple hops together (server A to server B to server C to server D ...)

See also:

  • Since this was posted, ssh evolved to include a -W <host>:<port> option, that avoids the use of nc. – Alex Stragies Apr 16 '17 at 16:19
  • @AlexStragies: Good point. I'll check when this was added and edit. Oh, and there's now -J (or ProxyJump) which makes this even easier; but that's only in OpenSSH 7.3 and up. – Piskvor Apr 18 '17 at 9:08

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