SSH Tunnels

Tunnel types and how to use it

• Dynamic
• Local
• Remote

Dynamic

I’m in Singapore and let’s say I want to watch Netflix US content.

Sample Environment
Singapore
Public IP      = 23.51.137.110
Private IP     = 192.168.1.23
SSH Server     = Disabled
User ID        = kevin
Port Forwarded = None 
US
Public IP      = 74.125.200.103
Private IP     = 192.168.2.34
SSH Server     = Enabled
User ID        = ubuntu
Port Forwarded = 22

SSH tunnel command will be like below assuming I wanted to use port 3128

ssh -D 3128 ubuntu@74.125.200.103

Once connected, configure Firefox network settings

I prefer to use Firefox for this because if I were to use Chrome or Safari, then I would have to configure my macOS system preferences. With this my Firefox will be using a US connection.

Local

I have a MySQL DB server in US running at port 3306 but only port 22 is exposed to the internet.

Singapore
Public IP         = 23.51.137.110
Private IP        = 192.168.1.23
SSH Server        = Disabled
User ID           = kevin
Port Forwarded    = None
US
Public IP         = 74.125.200.103
Private IP        = 192.168.2.34
SSH Server        = Enabled
User ID           = ubuntu
Port Forwarded    = 22
MySQL Server Port = 3306

SSH tunnel command will be like below assuming I am using port 6033 in Singapore to connect to my MySQL server in US running at port 3306

ssh -L 6033:74.125.200.103:3306 ubuntu@74.125.200.103

Once connected you can connect to your MySQL server as though it is running locally in your machine at port 6033.

Remote

Say I have a Ubuntu machine running at home acting as a file server and this machine has internet access but has no ports forwarding to it. I wish to get some files from it in the internet cafe.

Home
Public IP         = 23.51.137.110
Private IP        = 192.168.1.23
SSH Server        = Enabled
User ID           = home
Port Forwarded    = None
Singapore
Public IP         = 184.29.23.22
Private IP        = 192.168.2.34
SSH Server        = Enabled
User ID           = ubuntu
Port Forwarded    = 22
Internet Cafe
Public IP         = 23.49.29.121
Private IP        = 192.168.3.45
SSH Server        = Disabled
User ID           = cafe
Port Forwarded    = None

From the machine at home, a remote tunnel needs to stay connected all the time with the command below to the publicly exposed machine, assuming I’m using port 1234.

ssh -R 1234:127.0.0.1:22 ubuntu@184.29.23.22

From the internet cafe machine, SSH into the publicly accessible Singapore SSH server. From within the server SSH locally using port 1234.

ssh ubuntu@184.29.23.22

Then from within the machine run

ssh -p 1234 home@127.0.0.1

If the machine connecting remotely is a MacOS and the idle SSH connection disconnects frequently. Try adding these into ~/.ssh/config

Host *
    ServerAliveInterval 30
    ServerAliveCountMax 2

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