Getting external IP address

[Duncan Booth]

Paul Rubin <http://phr.cx@NOSPAM.invalid> wrote:

> Duncan Booth <duncan.booth at invalid.invalid> writes:
>> If you try connecting to 'www.showmyip.com' and requesting '/xml/' it 
>> should work.
> 
> If the firewall is really obnoxious, it can bounce consecutive queries
> around between multiple originating IP addresses.  That is uncommon
> but it's been done from time to time.

Yes, each connection through the firewall needs to have a unique 
originating ip and port number. If there are too many machines inside the 
firewall then you may need to allocate multiple ip addresses on the 
outside. I would hope that in general a single internal IP should map to 
one external IP at a time (otherwise you would have problems with ip based 
session persistence connecting to load balanced systems), but you might 
expect to bounce round different IPs after periods of inactivity.

Also you could have multiple levels of NAT in which case the question 
becomes whether Steven wants the IP as seen from outside the immediate 
firewall or outside the final one. Maybe he should be using IPv6 to avoid 
all this?