So if you were to make another connection, you will see an additional netstat entry with another local port generated for the second connection. This allows for multiple connections to be forwarded through port 4001. The SSH client is forarding traffic over local port 4001 to randomly selected open local port 64356 which is then sent over the SSH tunnel, which eventually lands at 192.168.20.10 port 22. Observe the output:Įvery 2.0s: netstat -abn | grep 4001 My-Cool-Macbook.local: Mon Sep 16 16:08:03 2019 This will run the command every 2 seconds and print the output to the screen. If you are curious about what your system is doing from a network perspective, open a separate terminal and run the following command before you create the SSH tunnel: This is useful if ssh is going to ask for passwords or passphrases, but the user wants it in the background. -f is optional, requests ssh to go to background just before command execution.This is useful for just forwarding ports. -N is optional, tells ssh to not execute a remote command.You could also use localhost in place of 127.0.0.1, assuming you haven’t modified that entry in your /etc/hosts file. Any connections to 127.0.0.1 on port 4001 will be forwarded to 192.168.20.10 on port 22 through the SSH tunnel. Typically, this will be 22, however there could be some security controls in place that do not allow SSH on the common port. It tells ssh to establish the tunnel on the remote port (destination port) 20622. 172.18.50.100 is the SSH server that we will be connecting to.username is the username to log into the jump host.ssh is the command we are using for our ssh tunnel.Access a network device/server that is only accessible via a jumphost You specify a local port for SSH to listen on, such as 4001, and all connections destined for port 4001 will be tunneled via SSH to a specified remote port, such as 22.
What is an SSH Tunnel?Īn ssh tunnel aka ssh port forwarding, allows an encrypted tunnel to be established over an untrusted network between an SSH Client and SSH server. However, as long as you have access to the jumphost, you may be able to use an ssh tunnel to mimic being directly connected to a network with access to the otherwise inaccessible hosts. Do you have a network device or server that can only be reached behind a jumphost? This is not an uncommon scenario, as security best practice often requires such.
0 kommentar(er)
