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We have a serverA to connect to. Then we use serverA to connect to databaseB. Setup like this in Putty (windows):

1. connect to admin@serverA
2. setup tunnel local port 10022 to databaseB:22
3. run 'vi'

1. connect to admin@localhost:10022
2. setup tunnel local port 1521 to database 1521
3. run 'vi'

(vi is used to hold session)

Then program use localhost:1521 for database connection.

I wonder if I can do it in a single command or a batch file in cygwin? Note that I cannot open port on serverA

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migrated from Mar 6 '11 at 10:11

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ssh -L 1521: admin@serverA ssh -L 61521: admin@databaseB

or using plink (Putty link) from a command window:

plink -ssh -L 1521: admin@serverA ssh -L 61521: admin@databaseB
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As to running this as a single command, the previous answer is correct but if the second ssh requires a password, it will probably not work (depending on ssh default configuration). You will have to force the allocation of a pseudo-tty by using the -t option, as in:

ssh -t -L 1521: admin@serverA ssh -L 61521: admin@databaseB

(this works using cygwin's ssh command)

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I'd try running:

ssh admin@serverA -L 10022:databaseB:22
ssh admin@localhost -p 10022 -L 1521:database2:1521

But man, I cringe even suggesting it. The people who firewalled off DatabaseB probably had a good reason for doing so. Talk with them.

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You can use the ProxyCommand option for that. Put the following into your ssh configuration file (which is usually at ~/.ssh/config):

Host direct-serverB
ProxyCommand ssh admin@serverA ssh admin@serverB sshd -i

Then you can connect to the serverB as if it was directly available:

% ssh -L 1521:localhost:1521 admin@direct-serverB

This command does not open any ports on the intermediate serverA. However, it has a drawback that you need to authenticate to serverB both from serverA and from your local machine.

If the serverA has netcat installed, then you could write this into your ssh config:

Host direct-serverB
ProxyCommand ssh admin@serverA nc -q0 serverB 22

and drop the serverA→serverB authentication step.

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