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I want to ssh into a server at my home which is behind NAT enabled router from my laptop when I'm away, say whlie using a public wifi.

Obviously, neither local nor remote port forwarding will work. But, I think it would work if I could somehow configure my router to relay packets coming from WAN and addressed to a specific port 22 to my server. But, I am not sure if that's possible.

Checking open ports on the public ip of my gateway, I can see only some known ports like 21, 22, 80 and non of others including 53, 110 etc.

Added: I forwarded the port 22 on my router to my server and tried to ssh into the server. I was prompted for the password but it replied, "Permission denied, please try again".

Another observation: router's WAN side IP doesn't match the public IP. I think that means my ISP doesn't provide me no public IP. What does it mean? Am I out of luck?

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  • You can check whether or not the WAN address should be accessible by referring to RFC 1918. Essentially, if the WAN address is in any of the ranges 192.168.*, 172.12-16.*, or 10.* then it's not publicly accessible. If in doubt, consider updating your question to include at least the first three octets (numbers) of the WAN IP address you're concerned about.
    – Chris Davies
    Jan 21, 2016 at 0:23
  • Yup, WAN address is 10.5.186.91 which is private address.
    – Bibek_G
    Jan 21, 2016 at 1:39
  • You might be able to run an old-style peer to peer OpenVPN connection between them, and then you can ssh over that
    – Chris Davies
    Jan 21, 2016 at 8:14

1 Answer 1

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You need to do the following things:

  1. ROUTER : check, what connection is open on port 22 of you router. if it is ssh-access to the router itself, you may disable this b)
  2. ROUTER : redirect it (forward port 22) to the servers's ip-address
  3. SERVER: remember to enable the servers ssh-d on the lan side, and test correct ip-routing from the server to the internet

or, of closing open port 22 on the router is not possible

  1. ROUTER : add a port forward of (lets say port 2222) to port 22 of your servers ip
  2. --

  3. like above

  4. ssh-connect to the routers public ip with the newly forwarded port 2222.

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  • I forwarded port 22 of router to that of my server. sshd is up and running on server and server is connected to the internet. Now when I try to ssh into public ip of the router at port 22, I get prompted for the password for the user. After providing the password, I get "permission denied, please try again". I get thrown out on third try. What might be the problem?
    – Bibek_G
    Jan 20, 2016 at 9:25
  • I edited my question.
    – Bibek_G
    Jan 20, 2016 at 11:23
  • a) verify that you really log on to the server, not the router by viewing /var/log/auth.log. b) ssh in from the local net to verify the password is the correct one. c) use pubkey auth when done (ssh-copy-id ..)
    – gerhard d.
    Jan 20, 2016 at 12:52
  • a)there's no /var/log/auth.log. Server uses Systemd not sys-v, I don't know the equivalent file. b) password is correct. c) I can use pubkey from local connection, but gives me same error on connection from outside.
    – Bibek_G
    Jan 20, 2016 at 13:39
  • check "/etc/hosts.allow" and "/etc/hosts.deny", if these allow or deny hosts from outside. from my point of view, you are forwarded to the wrong host. maybe you try rebooting the rooter? note: the init mechanism (sysv/systemd) has nothing to do with system logging in the first place. try to find out which syslog facility the sshd uses (/etc/ssh/sshd_config), where the log goes to (/etc/rsyslog.d/*), and look at the log while trying to log on.
    – gerhard d.
    Jan 20, 2016 at 13:56

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