ssh

The host rosa is in a network form which i will browse. You can connect rosa via ssh.

ssh -D 8080 user@rosa

You should configurate the local browser network connections. The browser send all request to localhost on port 8080. SSH sends the request direct to rosa. Everybody see, that you work on rosa.

The host newmax is behind a firewall and can't connect from internet. The host presura is outside the firewall and can connect from internet. You have an account on newmax and presura.

Type on newmax and connect to user1 at presura:

ssh -N -R 2222:localhost:22 user1@presura

At this time, the host newmax is at presura on Port 22.

Type the following lines on presura and connect to user2 at newmax:

ssh -p 2222 user2@localhost

Now, you work on remote newmax but you are at the local presura.

You can build a ssh connection to presura. The host presura functions in this constellation only as relay.

                                                        Firewall |                                                       
                                                 ____________    |        ____________                                   
 [1]                                            |            |   |       |            |                                  
  ssh -N -R 2222:localhost:22 user1@presura --->|----------->|---|------>|22:sshd ... |                                  
                                                |            |   |       |          : |                                  
                                                |   newmax   |   |       |  presura : |                                  
                                                |            |   |       |          : |    [2]                           
                                                |     sshd:22|<--o-------|<-------2222|<--- ssh -p 2222 user2@localhost  
                                                |____________|   |       |____________|                                  
                                                                 |                                                       
                                                                 |

With the -L option you can create a port forwarding at pressura:

ssh -N -L 2222:localhost:22 user1@presura.example.com

The option -N avoid a open terminal on presura.

Now, we type:

ssh -L 2222:sshhost.inside.localweb:22 user@gateway-to.inside.localweb

Then type on other terminal:

ssh -p 2222 user@localhost

Now you are on sshhost.

VPN connects networks, ssh connects only hosts.

             |            |                             
             |  Internet  |                             
    miles----|------------|-2222-gatekeeper---sshserver 
     \       |FW        FW|                        /    
      \      |            |                       /     
       -2223-|------<-----|-----------------------      
             |            |                             

ssh -p 2222 -L *:2223:sshserver:2222 user@gatekeeper