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I have drawn some sketches

##I have drawn some sketches TheThe machine, where the ssh tunnel command is typed is called »your host«.

##Introduction

Introduction

  1. local: -L Specifies that the given port on the local (client) host is to be forwarded to the given host and port on the remote side.

    local: -L Specifies that the given port on the local (client) host is to be forwarded to the given host and port on the remote side.

    ssh -L sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the local sourcePort to port onPort on the machine called forwardToHost, which can be reached from the connectToHost machine.

  2. remote: -R Specifies that the given port on the remote (server) host is to be forwarded to the given host and port on the local side.

    ssh -R sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the remote sourcePort to port onPort on the machine called forwardToHost, which can be reached from your local machine.

ssh -L sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the local sourcePort to port onPort on the machine called forwardToHost, which can be reached from the connectToHost machine.

  1. remote: -R Specifies that the given port on the remote (server) host is to be forwarded to the given host and port on the local side.

ssh -R sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the remote sourcePort to port onPort on the machine called forwardToHost, which can be reached from your local machine.

##Additional options

Additional options

Your example

##Your example TheThe third image represents this tunnel. But the blue computer called »your host« represents the computer where someone starts the ssh tunnel, in this case the firewalled machine.

##I have drawn some sketches The machine, where the ssh tunnel command is typed is called »your host«.

##Introduction

  1. local: -L Specifies that the given port on the local (client) host is to be forwarded to the given host and port on the remote side.

ssh -L sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the local sourcePort to port onPort on the machine called forwardToHost, which can be reached from the connectToHost machine.

  1. remote: -R Specifies that the given port on the remote (server) host is to be forwarded to the given host and port on the local side.

ssh -R sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the remote sourcePort to port onPort on the machine called forwardToHost, which can be reached from your local machine.

##Additional options

##Your example The third image represents this tunnel. But the blue computer called »your host« represents the computer where someone starts the ssh tunnel, in this case the firewalled machine.

I have drawn some sketches

The machine, where the ssh tunnel command is typed is called »your host«.

Introduction

  1. local: -L Specifies that the given port on the local (client) host is to be forwarded to the given host and port on the remote side.

    ssh -L sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the local sourcePort to port onPort on the machine called forwardToHost, which can be reached from the connectToHost machine.

  2. remote: -R Specifies that the given port on the remote (server) host is to be forwarded to the given host and port on the local side.

    ssh -R sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the remote sourcePort to port onPort on the machine called forwardToHost, which can be reached from your local machine.

Additional options

Your example

The third image represents this tunnel. But the blue computer called »your host« represents the computer where someone starts the ssh tunnel, in this case the firewalled machine.

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erik
erik
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##I have drawn some sketches The machine, where the ssh tunnel command is typed is called »your host«.

ssh tunnel starting from local

ssh tunnel starting from remote

##Introduction

  1. local: -L Specifies that the given port on the local (client) host is to be forwarded to the given host and port on the remote side.

ssh -L sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the local sourcePort to port onPort on the machine called forwardToHost, which can be reached from the connectToHost machine.

  1. remote: -R Specifies that the given port on the remote (server) host is to be forwarded to the given host and port on the local side.

ssh -R sourcePort:forwardToHost:onPort connectToHost means: connect with ssh to connectToHost, and forward all connection attempts to the remote sourcePort to port onPort on the machine called forwardToHost, which can be reached from your local machine.

##Additional options

  • -f tells ssh to background itself after it authenticates, so you don't have to sit around running something on the remote server for the tunnel to remain alive.
  • -N says that you want an SSH connection, but you don't actually want to run any remote commands. If all you're creating is a tunnel, then including this option saves resources.
  • -T disables pseudo-tty allocation, which is appropriate because you're not trying to create an interactive shell.

##Your example The third image represents this tunnel. But the blue computer called »your host« represents the computer where someone starts the ssh tunnel, in this case the firewalled machine.

So, ask someone to start a ssh tunnel connection to your machine. The command should basically look like

ssh -R 12345:localhost:22 YOURIP

Now the tunnel is opened. You can now connect via ssh to the firewalled machine through the tunnel with the command

ssh -p 12345 localhost

which will connect to your own localhost (your machine) on port 12345, but port 12345 is forwarded through the tunnel to port 22 of the localhost of the firewalled computer (i.e. the firewalled computer itself).