topic Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port in Tech Help - Software/Hardware etc

TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 08:19:45 GMT

I have recently purchased a TP-Link AC750 router and I'm using ,y old plusnet router in bridge mode (thanks to useful information found in this forum).

I am trying to run SSH on a machine on my local WAN. Port forwarding works fine (i.e. I can SSH into the local machine) when I open port 22. However, when I try to run SSH on another port, attempts to connect to the machine times out - and it looks like the port is not open (I can't see it when I use the service canyouseeme.org).

Does anyone know how I can configure port forwarding on the TP-Link AC50 router, so that I can run SSH on a non standard port?

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

SpendLessTime — Sat, 06 Aug 2016 08:37:07 GMT

Assuming you are using "Forwarding -> Virtual Servers", what happens if you add an entry like

Service Port = 22000
Internal Port = 22
IP Address = 192.168.x.x - The IP address of the PC running the service application.
Protocol = ALL
Status = ENABLED
Common Service Port = "--- select one--"

http://www.tp-link.com/en/faq-72.html

http://www.tp-link.com/en/faq-742.html

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 09:19:30 GMT

Hello, thanks for your quick response. I tried the parameters you provided, but the connection still times out (using http://canyouseeme.org).

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 09:22:18 GMT

BTW, I am running the SSH daemon on the non standard port, so I'm not sure your suggestion would have worked, although I suppose the first check/test is to see whether the port was open in the first place.

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

SpendLessTime — Sat, 06 Aug 2016 10:12:26 GMT

So you set the internal port to your SSH nonstandard port?

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 10:15:39 GMT

Actually, no. I left it blank - as it says that if the field is left blank, the same port number is used for the internal port

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

SpendLessTime — Sat, 06 Aug 2016 10:18:31 GMT

Might be worth a try setting it, it won't harm it as it's not working yet

Does the SSH work on the local IP address?

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 10:51:24 GMT

The field is actually auto populated (to match the external port number) if left blank.

Interestingly though,I can't SSH to the computer using the non standard port (I should have thought of trying this first).

I have checked using ps and telnet and netstat, to confirm that sshd is indeed running on the specified port, so I have NO idea as to what is causing this problem...

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 10:53:36 GMT

BTW, my laptop is connected to the LAN via WiFi, not a physical cable (I don't know if thats the reason I couldn't ssh into the desktop machine - even though their both on the same LAN).

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

SpendLessTime — Sat, 06 Aug 2016 11:09:37 GMT

Assuming it's Linux based, is something in the iptables blocking access to that port?

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 11:52:00 GMT

I ran sudo iptables -L | grep <port number>

No rule exists for that port. So no, no IP table rules relate to that port. There must be something wrong, I just can't put my finger on it..

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

SpendLessTime — Sat, 06 Aug 2016 12:13:38 GMT

Anything in the log files to even show an attempt to connect to the sshd port?

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 12:22:31 GMT

Thanks for trying to help. This is getting more intricate than I thought ...

Here are the last lines of /var/log/auth.log:

707 Aug 6 13:17:03 jupiter sudo: morpheous : TTY=pts/14 ; PWD=/home/morpheous ; USER=root ; COMMAND=/bin/grep sshd.*Failed /v
2708 Aug 6 13:17:03 jupiter sudo: pam_unix(sudo:session): session opened for user root by morpheous(uid=0)
2709 Aug 6 13:17:04 jupiter sudo: pam_unix(sudo:session): session closed for user root

HTH

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

SpendLessTime — Sat, 06 Aug 2016 13:33:48 GMT

Depending on which Linux distro you're using, this may work (if your distro uses systemd)

journalctl _COMM=sshd -f -n 100

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

MJN — Sat, 06 Aug 2016 17:58:02 GMT

Try SSHing to localhost on the alternative port and only if that works start to work outwards...

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 18:41:44 GMT

Sorry, I'm running Ubuntu 14.0.4 LTS (no systemd). I may well upgrade to 16.0.x LTS this weekend (I've been meaning to do that for a while now).

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 19:04:52 GMT

@MJN

This is what I have done (at the terminal of the desktop machine physically attached to the router):

1. /etc/ssh/sshd_config modified to specify new port number

2. Restarted sshd service

3. Used nmap -p <port number> --open -sV 192.168.0.0/24 to check that SSH is running on the specified port

when I attempt to ssh on the desktop machine (connected to the router):

ssh -p <portnum> morpheous@local_ip_address

I am able to login.

HOWEVER, when I attempt to run the same command (ssh) on my laptop machine (which is connected to the LAN via Wifi), the connection times out.

ssh

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

MJN — Sat, 06 Aug 2016 19:11:37 GMT

Can you ping the desktop from the laptop (to prove network connectivity)?

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

m0rphe0us — Sat, 06 Aug 2016 19:49:30 GMT

@MJN Yes. I can ping the desktop from the laptop. No packets lost

Re: TP-Link Archer AC750 port forwarding SSH connections using non-standard port

MJN — Sat, 06 Aug 2016 19:54:22 GMT

Something doesn't sound right. If you change the port back to 22 does it start working again? How about a different port?