logging ip addresses behind proxies

I'm trying to log my visitors' proxies via $_SERVER[REMOTE_ADDR]; but a lot
of users use ISPs that require them to use the ISP's proxy. The proxy
address is the one that is returned by the aforementioned server variable,
but is there a possibility to get the actual IP?


..soma

Titus A Ducksass <me@neverumind.com> wrote in message
news:<m1ghivkrhaqvblpjknqrenaj525ac41evp@4ax.com>. ..
>
NC> In the extreme (but not so rare these days) case, you can have a
NC> situation when a DSL/cable provider assigns a dynamic IP address
NC> to a local network, and local network's DHCP server assigns dynamic
NC> IP addresses to local machines. So today you have a machine whose
NC> IP address is 192.168.0.3 behind a proxy whose IP address is
NC> 100.99.98.97. Tomorrow the same machine can become 192.168.0.22
NC> behind 100.99.98.14 or something along those lines...
>
> The IP address will still be unique at that moment in time and can be
> traced via the ISP if needed.

Yes, but there's no guarantee it won't change in two seconds or
two minutes. Moreover, in the setup I described above, there is
a good chance it will change within two hours (most cable/DSL
providers seem to reassign IP addresses every 90 to 120 minutes).

Cheers,
NC