I'm trying to run my first Web server under Windows 2000. After I registered the domain with the InterNIC, I can access the site by IP address but not by DNS name. If I use a host-header-style setup in IIS, the site isn't even available by IP address. I'm using the default Web site. The Win2K domain is abc.com, but the registered DNS is xyz-web.com. Does the name difference have anything to do with it?
You can give your Web site a completely different domain name from your Win2K domain. In fact, you can make a good argument that the names need to be different so that users can't easily access your domain controller with less-than-helpful intentions. Because DNS is such a vital part of Win2K, naming a Win2K domain controller is much more important than it was with Windows NT 4.0.
Your problem is likely with the DNS server for your Web site. IIS administration books and training often overlook this problem, but the DNS server is clearly important to the effective operation of Web services. The first step to solving this problem is to register the domain. (If your Web site is http://www.abcdef.com, your domain is abcdef.com.) If you haven't registered a domain before, do so just to know what the process is. Prices range from $30 to $75 annually for the service. You can find a list of official registrars at http://www.internic.net/
regist.html.
When you register a domain, you must provide the name and IP address of a primary and secondary DNS server. The primary DNS server is one that is "authoritative" for your domain, which means that it contains the Start of Authority record for your domain. Very often, this name server is the same one that contains the entries that associate your Web site with an IP address. In this case, the authoritative name server points to itself as the place for hosts in the domain to go for the IP address. Technically, the name server record points to itself.
Here's a quick overview of the process. Jane wants to place a $10,000 order with http://www.abcdef.com, so she types that address in her browser. (As the IIS administrator, you really want Jane to find the domain!) Typically, Jane's system needs to reference a DNS server to resolve http://www.abcdef.com to an IP address. Her system uses the DNS server that is set up in her TCP/IP settings. Informing Jane's TCP/IP setup of the IP address for a DNS server can be done manually, but generally, DHCP provides the DNS server address to a client computer. As it turns out, the DNS server that Jane is using has never heard of http://www.abcdef.com, so it can't provide an IP address. The DNS server now goes to work to resolve the name for Jane. The server queries other servers and, eventually, queries the DNS servers of the .com domains themselves (called root name servers). The .com root name servers contain the names and IP addresses of all authoritative name servers in the .com namespace. How does the DNS server know where to find the root name servers? The server names and IP addresses of the root name servers are well known and are installed with the DNS server.
Now, let's get back to our story. The root name server for the .com addresses provides the IP address of the authoritative name server that you provided for your domain. So, now the DNS server conducting the inquiry (the one that Jane's PC originally queried) asks the authoritative server for the IP address of a host called www in the domain abcdef.com. The querying DNS server receives the IP address of the Web server, which in turn hands the address back to Jane's computer. Her browser then connects with the Web server, and the company is $10,000 better off.
The great thing about DNS is that this process occurs quickly; your typical user has no idea it's going on, which is why you need to understand this process thoroughly. The definitive book on the topic is Paul Albitz and Cricket Liu, DNS and BIND (O'Reilly and Associates, 1998). Although the book focuses primarily on UNIX, DNS works the same in Windows, and the book is much easier to read than most technical books. It also helps you get a handle on what is different about Win2K DNS, and an understanding of the difference is essential to supporting Win2K networks. Go to http://
www.dns.net for details about DNS.
So, now to your original question: What if this doesn't work? How can you tell what the problem is? Is it the Web server or DNS? To test DNS resolution, follow these steps:
- On the PC from which you're accessing the Web site, ping the Web site by name--in this case, www
.abcdef.com. (If you're working behind a proxy server, this process is more complicated because you can't ping from there.)
- If the resulting IP address is the IP address of your Web server, your Web site is set up on the default Web site, and you aren't using host headers, then you should be able to enter the name in step 1 and access the Web site. Otherwise, carefully check your IIS setup for the site. Make sure the Web services are running. From your browser, try accessing the site by IP address to eliminate name resolution as a problem.
- If you received the wrong IP address, you have to update your DNS server. If you received the message Host not found, then your DNS server has no entry for your domain and can't find a DNS server that does. In this case, use ipconfig /all (Win2K or NT 4.0) or winipcfg (Windows 9x) to obtain the IP address of the DNS server you're using. (If you don't have one listed, that is most likely the problem.) Compare that address with the name server IP address that you registered as authoritative for your domain. If they aren't the same, go into your TCP/IP properties and enter the IP address of the authoritative DNS server; make sure this address is the first or only entry. (You might need to reboot your system depending on the OS you're using.)
- Ping the Web site again. If you still don't get the correct IP address, the problem is with the DNS server entries for your domain. You can take this one step further on a Win2K or NT PC by using Nslookup as follows:
- At a command prompt, type nslookup. You'll connect with the first DNS server in your TCP/IP properties.
- Type the complete name you're trying to find (e.g., www.abcdef.com). This process returns the correct address for the Web site.
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