In this answer I will go through a concrete example. In your cast, replace localhost in the example with host2 and host with host1. Remote port forwarding does the opposite: it forwards traffic coming to a remote port to a specified local port.įor example, if you issue the command ssh2 -R 1234:localhost:23 traffic which comes to port 1234 on the server (host) will be forwarded to port 23 on the client (localhost). In this case localhost therefore refers to the server (host) itself. Note that localhost will be resolved by the sshdserver after the connection is established. Local port forwarding forwards traffic coming to a local port to a specified remote port.įor example, if you issue the command ssh2 -L 1234:localhost:23 traffic coming to port 1234 on the client will be forwarded to port 23 on the server (host). They are also called outgoing and incoming tunnels, respectively. There are two kinds of port forwarding: local and remote forwarding. You should be able to use port forwarding to access a service on host2 from localhost. $ sftp hop3 # for file transfers between your PC and host3 $ sftp hop2 # for file transfers between your PC and host2 $ sftp hop1 # for file transfers between your PC and host1 three steps)Īnother cool thing about the ~/.ssh/config file is that this will also enable sftp file transfers via any series of hops, e.g. $ ssh hop3 # will go from your PC to host3 via host1 and host2 (i.e. $ ssh hop2 # will go from your PC to host2 via host1 (i.e. $ ssh hop1 # will go from your PC to host1 in a single step Host hop1įrom your computer, you can test each jump individually, i.e. The ProxyJump keyword is used to specify an intermediate host is needed to arrive at the target host. I can use ~/.ssh/config config file which contains the details of each host and all identities needed to access each host on my host PC. If I want to use a single ssh command to go from your PC to any of the hosts. To get to the final computer I may have used multiple ssh commands and the identity files are stored on multiple computers: $ ssh -p 22 -i ~/.ssh/pem/identity1.pem To illustrate this, suppose I needed to get to a destination in 3 hops, and, for each hop, I needed to specify username, host, port, and identity. My answer is really the same as all the other answers here, but, I wanted to clarify the usefulness of ~/.ssh/config and ProxyJump. To access port 8080 on HOSTC via HOSTA and HOSTB: mssh HOSTA HOSTB -L8080:HOSTC:8080 To access HOSTC via HOSTA and HOSTB and use non-default SSH-portnumbers and different users: mssh access HOSTC via HOSTA and HOSTB and use X-forwarding: mssh HOSTA HOSTB HOSTC -X To access HOSTC via HOSTA and HOSTB (same user): mssh HOSTA HOSTB HOSTC $cmd = "ssh $localhost -p $iport -o UserKnownHostsFile=/dev/null -o StrictHostKe圜hecking=no" As a result, the first ssh command keeps the tunnel open until the following two conditions are satisfied: sleep 10 is finished and the tunnel is no longer used.Īfter reading the above and glueing everything together, I've created the following Perl script (save it as mssh in /usr/bin and make it executable): #!/usr/bin/perl Usually, the first ssh command would close after 10 seconds, but during this time, the second ssh command will have established a connection using the tunnel.
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