Local TCP forwarding is a local port forwarding to a remote server.We suggest you use it only temporarily, and use proper firewall rules to access your applications on productions servers.Here are the typical usage scenarios of SSH tunneling: Therefore we urge you to use caution when using this feature. Also it could violate your organization’s cyber security policies. While SSH port forwarding enables us to access remote ports via a SSH tunnel, it could cause security vulnerabilities. To access Event Log, right click top menu bar, and click Event Log, after opening the SSH session to server.Ī successful port forwarding will look like this. If you encounter any problems, you can have a look at PuTTY Event Log. Note that the destination in PuTTY configuration for this case should be y.y.y.y:3100 As long as y.y.y.y is reachable from x.x.x.x, we can access app running on server 2, via server 1. We can also use SSH port forwarding to access a port on a remote machine as below. In some cases the app may be listening only on server’s private IP address x.x.x.x, so that you have to put x.x.x.x:3100 on the destination textbox in PuTTY configurations. įor the above port forwarding configuration to work, our app on the server must be listening to 127.0.0.1, which you can verify with ss -t state listening '( sport = 3100 )' ( more about ss command) Since our app is a HTTPS web application, we can access it with the URL. When SSH session is established, we should be able to reach port 3100 on the remote server via 127.0.0.1:3100. Save the configurations to session, and click Open to establish the SSH connection. Again note the 4L at the beginning of the configuration, which correspond with Ipv4 and Local. (Local and IPv4 should be selected)Ĭlick on Add, and you will get below. Note the configurations with the radio button in two rows. While most SSH clients support local port forwarding, we are using PuTTY, which is a free and popular SSH client software.Īssuming you already have the server IP address configured in PuTTY, go to Connection -> SSH -> Tunnels, and add following configuration. But, the SSH client in our laptop requires some configurations. Since the traffic to destination port 3100 is encapulated, our firewall will sess only traffic to port 22.įor local port forwarding to work, there are no specific configurations to be done at the server. In local port forwarding, traffic destined to a port (3100 in this case) on the local server is forwarded to the remote server via the SSH tunnel. (While it is possible to get the 3100 port opened from firewall, in a typical organization it is a cumbersome process.) The corporate IT firewall, sitting between the laptop and the server, is allowing only SSH traffic to pass through. Our laptop is running Windows OS, and the Linux server is running a web application over port 3100. Let’s see the typical scenario, where this would come in handy. This post focus on local port forwarding when the client is not a Linux machine. There are two types of port forwarding local, and remote. SSH port forwarding is a mechanism to send arbitrary traffic over an encrpted SSH tunnel. SSH port forwarding is a versatile feature.
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