Ssh tunnelling via intermediate host

I recently needed to copy files using scp, while not able to copy directly to the target host. I had to use an intermediate firewall host. There is a few ways to get this done and most requires netcat (nc) on the intermediate host for copying.

Keep in mind using -t for just a ssh shell connection will work:

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$ ssh -t rrosso@backoffice.domain.com ssh admin@10.24.0.200

If needing scp below is a way to get this done when netcat is not a possibility.

In a new terminal do this (command won”t return a prompt and leave the terminal open):

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$ ssh rrosso@backoffice.domain.com -L 2000:10.24.0.200:22 -N

In a new terminal ssh as follow:

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$ ssh -p 2000 admin@localhost

Scp as follow:

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$ scp -P 2000 testfile admin@localhost:/tmp

Sftp also possible:

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$ sftp -P 2000 admin@localhost

Update 1: Above will work fine but you can also consider the following to make things more transparent.

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$ vi .ssh/config
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Host *
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 ServerAliveCountMax 4
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 #Note default is 3
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 ServerAliveInterval 15
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 #Note default is 0
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#snip
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host work-tunnel
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 hostname backoffice.domain.com
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 port 22
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 # SSH Server
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 LocalForward localhost:2000 10.24.0.200:22
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 user rrosso
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# Aliases as follow
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host myhost.domain.com
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 hostname localhost
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 port 2000
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 user admin

Then run the tunnel connect first (use ssh -v while still troubleshooting):

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$ ssh work-tunnel

Leave above terminal open to leave tunnel going. And now you can run commands in new terminals with syntax as if no tunnel required.

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$ scp testfile myhost.domain.com:/tmp
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$ ssh myhost.domain.com

That should do it for a ssh shells.

Example for other ports:

Note you can do a lot of other ports also in similar fashion. Here is an example you could play with.

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Host workTunnel
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    Host ssh.domain.com
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    Port 5001
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    # SMTP Server
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    LocalForward localhost:2525 smtp.domain.com:25
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    # Corporate Wiki.  Using IP address to show that you can.
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    LocalForward localhost:8080 192.168.0.110:8080
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    # IMAP Mail Server
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    LocalForward locahost:1430  imap.pretendco.com:143
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    # Subversion Server
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    LocalForward locahost:2222  svn.pretendco.com:22
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    # NFS Server
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    LocalForward locahost:2049  nfs.pretendco.com:2049
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    # SMB/CIFS Server
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    LocalForward locahost:3020  smb.pretendco.com:3020
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    # SSH Server
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    LocalForward locahost:2220  dev.pretendco.com:22
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    # VNC Server
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    LocalForward locahost:5900  dev.pretendco.com:5900
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### Hostname aliases ###
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### These allow you to mimic hostnames as they appear at work.
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### Note that you don't need to use a FQDN; you can use a short name.
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Host smtp.domain.com
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    HostName localhost
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    Port 2525
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Host wiki.domain.com
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    HostName localhost
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    Port 8080
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Host imap.domain.com
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    HostName localhost
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    Port 1430
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Host svn.domain.com
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    HostName localhost
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    Port 2222
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Host nfs.domain.com
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    HostName localhost
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    Port 2049
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Host smb.domain.com
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    HostName localhost
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    Port 3020
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Host dev.domain.com
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    HostName localhost
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    Port 2220
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Host vnc.domain.com
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    HostName localhost
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    Port 5900