How to use ethernet for private lan and 3g for external network at the same time?

[pod]

On Fri, 2010-08-06 at 00:42 +0800, archayl wrote:
> My situation is:
> 
> I'm using ethernet connection in office to get the file sharing and
> other office related stuff working.
> 
> At the same time, I want to browse the internet using 3g modem (USB
> dongle). My workplace is using proxy to block connection to outside
> world. The only way to get access to the internet is through the 3g
> modem.
> 
> Currently, I have to switch off the ethernet to go to the internet, as
> my computer will utilise the available and already connected 3g modem.
> To get the office stuff working again, I need to turn on the ethernet
> and I lost connection to outside world.
> 
> Is there any way to get both working at the same time? I mean like when
> I type in address that is in Local Network, it'll use the ethernet.
> Else, it'll use the 3g connection.

Perhaps right-clicking the NM icon -> edit connections -> select the
correct wired connection -> edit -> IPv4 settings -> Routes... -> 'Use
this connection only for resources on it's own network' check box will
tell NM to route global traffic back to the 3g connection.

Word of warning though, getting caught using a modem while connected to
the office lan by high strung security obsessed network/IT guys might
mean losing your job.

Dave