Fw: Question about NAT|
"Paul Arch" <paul,AT,sdmgroup,DOT,com,DOT,au>|
Sun, 19 Oct 2003 11:03:48 +0800|
> > I have an embedded device out in the field which uses a GPRS
> > connection to establish a tunnel to a static IP.
> > REMOTE DEVICE <-------- NAT GW --------> Internet <--------- SERVER
> > (10.2.x.x) (Static IP)
> > As far as I know, the GPRS connection (its like WAP for mobile phones)
> > is provided via a NAT gateway. This is OK, and I can get everything
> > working fine using dynip and ping on the remote device. I have
> > thought of it as like a road warrier, except its natting its way to
> > the internet.
> > The thing is, cost for traffic is a big issue on GPRS - 2.2cents per
> > 1kB of information sent and received. And as far as I can tell, I
> > need to specify the ping on the Remote Device to update its changing
> > NATTED address - am I correct in this thinking ? Is there a way of
> > keeping the 'connection' open without requiring the ping ? I am
> > starting to think I can't since we are using UDP.
> You really only need to send something through the tunnel each
> time the public IP changes on the NAT gateway. This resets the
> peer address on the other end so it will be able to send back
> later. Can you detect the gateway IP change in some way that
> doesn't transmit data?
At the moment, I don't think I can :( I also don't know how often the
changes occur. I was going to have software running on the Server, that it
would ask for information off the Remote Device every 5 minutes. Now I am
thinking a better way might be for the Remote Device to check in the
information every 5 minutes - hence, if the addresses did change, it would
update that information to the Server - so I could still establish a
connection From the server to the Remote Device on demand.
I would love a solution that could detect gateway IP changes without data
Does anyone have any ideas ?