Re: External IP from internal?
- From: "Shenan Stanley" <newshelper@xxxxxxxxx>
- Date: Sun, 5 Nov 2006 17:38:15 -0600
brett wrote:
If I know the computer name of a machine on an intranet that I am
on, is there a way to figure out what IP that machine broadcast
over the Internet?
Shenan Stanley wrote:
That machine probably doesn't broadcast a public IP. The
NAT/router device it is attached to does - and traffic is managed
by that device and sent to the correct system behind it.
http://www.whatismyip.com/
That should give you the public IP of your network as a whole.
You would have to configure the router/NAT device to forward
certain traffic to the internal private IP address of the machine
in question - dependent on what you wish to do.
brett wrote:
Ok. I guess the person sitting at the machine in question could
just go to that site and get the external IP. The external IP on
my machine seems to always be the same. Are intranet machines
always going to have the same external IP?
Shenan Stanley wrote:
Not necessarily - depends on how the Internet Service Provider
treats that particular device - and what agreements the person who
owns that device (NAT/router) has with the ISP. If they have
purchased a static IP address - yes... It will remain the same. If
they have not - then it will USUALLY stay the same - but you have
no control over when it might change. It may stay the same for
days, weeks, even years.
Things you need to know...
The NAT/Router device will have to be configured to pass the ports
through to the proper internal IP address - or it will just block
any attempt to get to machines behind said device.
The software firewall on said machine must be set to allow the
traffic through - otherwise even if the router is configured
correctly to forward certain port requests - it will block it.
Most decent routers allow you to use free dynamic DNS services - so
you can assign an easy to remember address to the router and let it
maintain it for you. Also - if the IP address changes - the
Dynamic DNS service will keep up with that on a properly
configured/capable router.
What is it you are trying to do?
brett wrote:
I'm tracking visitors on a website. When some one from that
particular intranet visits the site, I want to know which person it
is. I know the user by the IP logged...for now. But it will be a
problem if the IP changes.
Well - that's a whole different issue.
What if you have a set of people visiting your site from behind a NAT
device?
Small example: I have 6 computers in my home. All behind a NAT device.
Your website would identify me as one user - one IP. Yet I have 6 machines
and who knows how many users per machine?
Larger example: I own a medium-sized business with 100 computers in one
location. They are all behind a NAT device. All 100+ users will be one
visitor to your site. You will know that someone from that IP visited, but
not who in particular.
Logons/Cookies may be a better method of tracking.
--
Shenan Stanley
MS-MVP
--
How To Ask Questions The Smart Way
http://www.catb.org/~esr/faqs/smart-questions.html
.
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