IP Technical question

[Dave Howe]

Peter Tomlinson wrote:
> My simple cable broadband connected situation with a low cost firewall
> router can certainly have many systems attached - I think mine has a
> local address range of around 200 nodes - and they are all seen as the
> same IP address when a web site tells the user of any one of the local
> systems what IP address it has. 

Many of my customers have hundreds, and in some cases, thousands of
seats - but only one web proxy server, and only one IP address from the
point of view of the outside world. This works fine - just like a letter
to a household will have <name><address> on it, so internet packets have
<port><address> on them. its the responsibility of the web proxy (or
whichever other machine ultimately "owns" the IP address) to know which
internal machine should be the recipient of any traffic that comes in
for any given port, which is otherwise just a number from 0->65535.

In most of those cases, the web proxy is there purely to hold a record
of which internal machine (identified by user name, not IP) requested a
given page. of course, there is no guarantee that that mapping is 100%
trustworthy, but given users are made aware that they are responsible
for any web access made from their username, they tend to be reluctant
to share :)