On 9/22/2010 8:22 PM, Elton wrote:
> About the initial question for the different external IPs: could we
> safely assume that my ISP has a double NAT configuration or is it
> something else that causes this behaviour?


It sounds like either double NAT or your host ISP is using some sort of
address scrambler in their router to ensure you can not host your own
server.

One way to usually identify double NAT is to open a command window, also
known as command.com in older versions of Windows.

With the command window open, try doing a route trace to a large
commercial organization, as in "tracert www.google.com", minus the quote
marks, and check the results.

If you see an address starting with any combination of the following
other than the very first entry then you are experiencing a double NAT
problem as these IP values are restricted from being routed directly
over the internet.

10.0.xxx.xxx
172.16.xxx.xxx
192.168.xxx.xxx

If not then the ISP must have something in your path that they are using
to actively randomize the route of your inbound address as a means of
blocking you from having a web server.

Usually I have seen that in locations where the host country is paranoid
about people running their own unmonitored web sites, like China or
North Korea.

I've run out of ideas and will bow out of the discussion so others can
be heard...