How to create a backup internet, for when your primary ISP fails ...

[newquestions]

Hello everyone,
Thanks for your time

I have a fairly unreliable primary internet connection ...

But I also have a reliable 3G "backup" mobile connection.
(I don't use this connection all the time, as it is bandwidth
limited, and quite a bit slower than my fixed ADSL service)

Is there a way to automatically switch
to my 3G backup when my primary ADSL internet service fails?

A few technical notes ...

My primary internet is ADSL, and I am connected to my router
via an ethernet cable. No special settings are used on my PC.
I'm just automatically grabbing IP and DNS from my router.

In terms of the 3G internet connection ... it originates from
a mobile 3G device, that throws out a WIFI signal. My PC
connects to it, via WIFI and once again - everything is
automated. IP and DNS etc. No special settings needed.

Does anyone know of any software, that monitors internet connectivity,
and can swap between pre-configured internet service providers?

So ... if my primary internet provider fails, and stops providing service,
then the software disconnects, and reconnects to my 3G connection?

Thanks so much for your time everyone

Cheers,
Johnathan

[traiz]

It sounds like you're looking for something like this
http://www.cisco.com/en/US/prod/collateral/routers/ps380/ps10082/data_sheet_c78_498096.html

There may be something you can do with open WRT, and a linksys router that can be flashed with it.

[newquestions]

I was more thinking about a piece of Windows software,
that simply checks for internet connectivity every say
60 seconds ...

And upon failure, disconnects the primary ISP,
and then attempts to reconnect my 3G connection.

Basically, both of my connections are handled by the
Windows "network and sharing center" - and both are
automated etc.

I was mainly interested in a software solution,
as opposed to a dedicated hardware scenario.

Thanks for your help

[d2dtk]

What if you connect the pc to wifi from phone and ethernet directly to modem? When modem goes offline computer should use wifi..