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Re: Establish an alternative connection to an embedded system

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From Andrzej Adam Filip <anfi@onet.eu>
Newsgroups comp.os.linux.networking
Subject Re: Establish an alternative connection to an embedded system
Date Sun, 22 Jun 2014 10:09:21 +0200
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perf60@gmail.com wrote:
> I have an embedded linux system on a remote farm. Usually I ssh into
> the system via the farms ADSL/WiFi system (using port forwarding). But
> sometimes the traffic on the farm blocks me from connecting.
>
> To solve this, I have added a GSM/GPRS modem to the system. The modem
> uses the gsmmux giving 3 channels /dev/mux0 thru /dev/mux2. I have a
> python daemon watching SMS messages om /dev/mux1. Then I can send an
> SMS telling this daemon to set up ppp on /dev/mux0. After the link is
> set up, the daemon answer the SMS telling me the IP number of the
> alternative link.
>
> Problem is, it does not work to ssh into this IP. Something is obviously missing in my setup - it only works from the system towards the internet.
>
> What must I do to enable ssh to access my system via this alternative connection?

1) Have you changed ListenAddress in /etc/ssh/sshd_config ?
2) Have you implemented source based TCP/IP routing to make _both_ links work
   at the same time? [unless your system is for monitoring only]
3) Have you used tcptracerourote to track TCP connections attempts?
   [ There may be a firewall in between ]
4) AFAIR some GSM internet providers block incoming TCP connections.
   You may try to overcome it by making outgoing ssh connection over GSM link
   with -R port forwarding

-- 
[Andrew] Andrzej A. Filip  -  https://www.linkedin.com/in/andfil

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Thread

Establish an alternative connection to an embedded system perf60@gmail.com - 2014-06-22 00:34 -0700
  Re: Establish an alternative connection to an embedded system Andrzej Adam Filip <anfi@onet.eu> - 2014-06-22 10:09 +0200
    Re: Establish an alternative connection to an embedded system perf60@gmail.com - 2014-06-22 01:46 -0700
      Re: Establish an alternative connection to an embedded system ein <ein@no.spam> - 2014-06-22 11:28 +0200
      Re: Establish an alternative connection to an embedded system ein <ein@no.spam> - 2014-06-22 11:36 +0200
        Re: Establish an alternative connection to an embedded system perf60@gmail.com - 2014-06-22 03:20 -0700
          Re: Establish an alternative connection to an embedded system Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2014-06-22 12:37 +0200
            Re: Establish an alternative connection to an embedded system ein <ein@no.spam> - 2014-06-22 13:45 +0200
              Re: Establish an alternative connection to an embedded system perf60@gmail.com - 2014-06-22 05:15 -0700
                Re: Establish an alternative connection to an embedded system Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2014-06-22 14:20 +0200
                Re: Establish an alternative connection to an embedded system perf60@gmail.com - 2014-06-22 05:46 -0700
                Re: Establish an alternative connection to an embedded system Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2014-06-22 15:05 +0200
                Re: Establish an alternative connection to an embedded system perf60@gmail.com - 2014-06-22 06:26 -0700
                Re: Establish an alternative connection to an embedded system Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2014-06-22 15:47 +0200
                Re: Establish an alternative connection to an embedded system perf60@gmail.com - 2014-06-22 07:02 -0700
  Re: Establish an alternative connection to an embedded system David Brown <david.brown@hesbynett.no> - 2014-06-22 14:45 +0200

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