Fast and dirty DNS and Hosts file FAQ.

Every computer connected to the internet has a numerical address (IP address). 255.23.156.98 is a typical IP address.

Your computer is connected to the internet and has a unique IP address. It probably changes every time you connect. (They get assigned to you from a pool your ISP has)

Servers are computers connected to the internet. They are just computers, like yours but nicer :-) They are built and configured to Serve up something to other computers that connect and ask. Web servers serve up web pages, mail servers serve up the mail, news servers serve up the news (UseNet), list servers serve up mailing lists, etc. The word "server" refers both to a computer and the software it is running (server software).

Servers, being computers connected to the internet, have IP addresses too. They don't change.

In order for one computer to talk to another on the internet they need to know each others IP address.

Web pages have names like www.great-web-page.com. This is because names are easy for people to read.

If you enter the name of some web page in your browser your computer needs to know the numerical address of the server where that web page lives (the host for the page).

DNS servers (Domain Name System) translate names into numbers. Your computer can go to one and request a lookup for some name. The DNS server then returns the IP address associated with that name and your computer happily trots off to that numerical address.

The numerical addresses of two DNS servers (a main one and a backup) are located on your machine somewhere. Your ISP provided them for you. You can use anybodies DNS servers (so long as you know their numerical addresses, no way to look up the address of the server that looks up the addresses).

You don't have to use DNS. You can enter the numerical address of a server in the address bar of your browser and you will go right there. How many numbers do you want to memorize?

If a web site (or mailing list) moves from one server to another then it has a new IP address associated with it's name. In order for you to find it (by name) the DNS servers have to be updated with the new info. (the things just have big lists of what number goes with what name and they literally look up the info when your computer requests it). It can take awhile for all the DNS servers in the world to get the word passed around among themselves about the new number for a particular name. This is the issue at hand with the IBMWR lists moving.

Your (Windows, I know zip about Macs) computer has a little DNS system built into it. It always checks its own list first when looking up an IP address for some name. If it doesn't have the info on board then it hits a DNS server on the web for a lookup. If it does have the info on board then it skips the DNS server and goes right to the address listed.

Your computer keeps it's own list in a file called Hosts. No extension, just Hosts. Find a file on your computer called Hosts and open it with a simple text editor (like notepad). Before you open it you might right click the name and see if it is read-only. If it is, uncheck that so you can make changes.

If you have a file called hosts.sam then that is a sample file. Open and read but make no changes.

If you do not have a hosts file you can make one. Just make a text file called Hosts and save it with no extension. You can also look for a program on the web called Hostess (and their are others). It is a hosts file editor.

Any line in the hosts file that starts with # will be ignored by the computer. This is handy for making notes for your self that you don't want your computer to read (and get confused by)

A "DNS" entry in the hosts file looks like the IP address followed by a few spaces followed by the name.
137.34.18.1    msgtag.com.
This entry pairs that IP number with the msgtag site. Just type what you want, make sure each entry is on it's own line (if you do several), save and close the file. Remember you are writing stuff for your computer to read. Computers are stupid. Make no typos. You won't break anything but if it is wrong you won't connect either.

Look for the name and IP address for our mailing list to put in your hosts file until the DNS servers update. This has been a bunch to read but if you are used to working with the hosts file it takes 15 seconds.

More Fun

You can do other things with the hosts file. You can block web sites and you can redirect.

Suppose you want to keep the kids from going astray on the web. You might put this entry in your hosts file:
127.0.0.1      www.HarleysAreSwell.org
That is a special IP address. It is called Local Host and it is an internal number used by your machine. It is one of a group of special numbers that cannot be used over the internet. You use them on private networks (like in your home or at work). When your computer tries to connect to www.HarleysAreSwell.org it will find the lookup in the hosts file, skip the web DNS servers and...uh...end up staring up it's own tailpipe. You will get a Site Not Found error :-) A lot of the anti-spyware programs (like SpyBot) use extensive lists of entries like this in the hosts file to block spyware sites.

You can also use the Hosts file to redirect. Perhaps someone is using your work computer to peruse the porn sites while you are at lunch. So you make an entry in the hosts file that has the offensive site name (www.PurePorn.com) paired with the numerical address belonging to some Fine Christian Organization on the Far Right. (You should have seen your face, Chuck!).