> To browse the Web from inside a Firewall your IP address will not appear in
> your packages, only the firewall's IP address. Since there is no WWW browsing
> without TCP/IP you would still have a IP address on the inside, but that might be
> one already in use on the Internet, nobody would notice.
The Internet Assigned Numbers Authority (IANA) has reserved the following
three blocks of the IP address space for private internets: (RFC 1918)
10.0.0.0 - 10.255.255.255 (10/8 prefix)
172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
192.168.0.0 - 192.168.255.255 (192.168/16 prefix)
Any private network that connects to the Internet through a Firewall or
an address translator is expected to use this private IP addresses. And
Internet routers are required to drop any datagram with private source
and/or destination IP address.
> >[log in to unmask]
> You can find the IP address very simple for the server eo.wn.apc.org
> (the simples I can think of is to use the "Ping" program), but you can
> not find the user's IP address unless you investigate the mail headers
> from him and find it there. And even then it is probably a temporary
> address as stated above.
If someones internet e-mail address is "[log in to unmask]" then
"eo.wn.apc.org" is a mail server or a mail gateway. Either ways, it needs
to have a permanent puplic IP address. It can not be temporary and it
should not be assigned by a DHCP. It should have be a static IP address.
Moreover, the mapping of a domain name to an IP address is static. But the
assignment of an IP address to a host can be temporary in the case of a
dialup connection. Even for hosts directly connected to a LAN, the IP
address may only be used for lease period if the IP address is assigned
by a DHCP server.
The problem with temporary IP address assignment is that it is difficult
to provide services (Web server, FTP server, mail server, etc.) since
you can not a fixed domain name.
In general, it is difficult for a server behind a firewall, to offer its
service to the Internet. Moreover, the Firewall requires regular update
evertime there is some change in some of the Internet protocols such as
HTTP, SHTTP, etc. Otherwise, hosts behind a firewall may not be able to
access some of the new service in the Internet.