See private IP's behind router

[DragonNOA1]

I noticed on the "Shields Up" website there was a way for them to see my private IP address. How can you do this? I've heard both things that your private IP is not transmitted and that it is transmitted over the internet. So which is it?

And more importantly, how can you find it out what someone's private ip is? Like if someone plugs in a router here at work, how can we figure it out that there are private IP's behind a rogue router and stop it from happening? TIA

 

[Malk-a-mite]

And more importantly, how can you find it out what someone's private ip is? Like if someone plugs in a router here at work, how can we figure it out that there are private IP's behind a rogue router and stop it from happening? TIA

http://www.cs.columbia.edu/~smb/papers/fnat.pdf

"There have been many attempts to measure
how many hosts are on the Internet. Many of those endpoints,
however, are NAT boxes (Network Address Translators),
and actually represent several different computers.
We describe a technique for detecting NATs and counting
the number of active hosts behind them. The technique is
based on the observation that on many operating systems,
the IP header’s ID field is a simple counter. By suitable
processing of trace data, packets emanating from individual
machines can be isolated, and the number of machines
determined. Our implementation, tested on aggregated local
trace data, demonstrates the feasibility (and limitations)
of the scheme."

 

[cyberjt]

One of the easiest ways is to use client side scripting to get the IP - of course whilst this may be harmlessly just displaying the information to you, it could then be used to populate a form which is then re-posted to a server.

 

[DragonNOA1]

Thanks for the first link. Good info there.

One of the easiest ways is to use client side scripting to get the IP - of course whilst this may be harmlessly just displaying the information to you, it could then be used to populate a form which is then re-posted to a server.

True, true. I was curious and it through me off guard at first. Thanks!