IP addresses on a LAN

[john fulgor]

Hello,
my configuration:

-ethernet LAN

-Various Red Hat 9/Windows XP PCs on the LAN

-One Windows XP PC is connected to the Internet via an ADSL modem,
Windows XP automatic LAN creation has been successfully run on this computer.

Result:

-All PCs of the LAN are assigned addresses like 192.168.0.xxx

-All PCs can connect to the Internet

-All PCs can connect between each other

And that's OK.

Now the questions.

1)What kind of addresses are 192.168.0.xxx? On what basis are they assigned? It seems to me they are local address... But if it were so, how can the LAN computers connect to the internet?

2)How can I use host names in place of IP addresses? They're not always the same for the same machine. If I assing a name to a Linux machine and try to connect to it from another, the name is not recognized, as if the correspondence name-IP adddress is not recorded anywhere.

Thank you in advance,
John

[Monkeh]

192.168.*.* addresses are internal addresses, yes. The machines access the internet by using your XP machine as a gateway (this automatic LAN creation software sounds like a DHCP server with a fancy interface to me), it records what sessions are opened by the LAN machines and then routes the correct data to them when received. I hope you're running a firewall on it

The names aren't stored by anything remote machines can access. If you keep the same IP address, but multiple names, as long as you don't use those names on other computers, you can add the IP to /etc/hosts with the names (192.168.0.6 home dell hello, as an example) on linux, and C:\WINDOWS\system32\drivers\etc\hosts on Windows, you can then use those names to access the machines.

[Xenon]

Just for information:
It seems you are using Internet Connection Sharing. This is whereby your XP machine takes the role of a DHCP server and allocates IPs to any clients requesting for an IP and also tells the clients to access the internet through the XP machine. The only limit of this is in the Microsoft license agreement which states that you are only allowed to do this for upto 10 computers and is the same if you are sharing a printer. If you want more clients and want to stay legal, you have to pay out to get a Microsoft server OS.

[drakebasher]

If you want more clients and want to stay legal, you have to pay out to get a Microsoft server OS.

Or setup a Linux machine as server.

[jeickal]

About the 192.168.*.* addressing:

If you want the full explanation you need to read the RFC1918 of the IETF.
RFC stands for "Request For Comments" and the IETF is the Internet Engineering Task Force, the folks writing the standards of all the protocols we enjoy everyday (TCP - IP - HTTP,...)
You can find the RFC1918 here ==> http://www.faqs.org/rfcs/rfc1918.html

If you're just looking for a quick summary, this is how I would put it:

There are some ranges of IP addresses that are reserved for private use in companies intranets or simply at home. Those ranges are not "routable" over the Internet, meaning that no web site can use them. Those addresses are:

10.0.0.0
172.16.0.0 up to 172.31.255.255
192.168.0.0

When you browse the Internet, people sees you with the IP of the side of your gateway pointing to your provider, usually called your "public IP". If you would like to know which IP is that, check this site out ==> http://www.ipchicken.com.

Even if you have several PC on your LAN, they will be seen with the same address from the Internet. The gateway is translating your IP into a this public IP, and performing some PAT (Port Address Translation). Basically if you surf on the same web site from 2 differents PC, your gateway will use 2 different TCP source port to keep track of the 2 differents HTTP session, each coming from a different PC.
Hope I'm clear... It gets quickly more complicated...

[Xenon]

Obviously there is the choice of the Linux server, I was merely stating what you would have to do, if for some strange reason you wanted to stick with Microsoft.