In your effort to become an MCSE under Windows 2000, you'll need to understand the inner workings of these three crucial services.

Service Station: DNS, DHCP, and WINS

In your effort to become an MCSE under Windows 2000, you'll need to understand the inner workings of these three crucial services.

• By Harry Brelsford
• 06/01/2000

Part of working with Windows 2000 Server is learning what to implement and what not to implement. This month I cover three services, DNS, DHCP, and WINS, all possible implementation candidates. Your server (and network) will run just fine without DNS, DHCP, or WINS installed, depending on your situation, so why would you want to run those services? Let's start with definitions.

Definitions

• DNS--The Domain Name System is the default name resolution mechanism for both Win2K Server and the Internet. It resolves host names (www.mcpmag.com) to TCP/IP addresses (209.27.114.5).

• DHCP--Officially known as Dynamic Host Configuration Protocol, DHCP is used in organizations to supply network connectivity. The DHCP service, commonly referred to as the DHCP Server, issues TCP/IP networking addresses. More on this in a minute.

• WINS--The Windows Internet Name Service is used to find network objects (like computers) when you're using NetBIOS naming (such as Machine01). Its roots date back to the NetBEUI protocol days (when NetBEUI was in favor). You might know it as the way computer names are displayed when you double-click My Network Places in Win2K or Network Neighborhood in Windows 98 and 95.

What These Services Do

DNS is actually pretty easy to understand. It's analogous to calling directory assistance to get a phone number. When you make this type of call, you typically communicate that you want to speak with John Smith in Placerville, California. The operator resolves the name John Smith in that location to a phone number such as 206-555-1212. Then you dial the number and you're connected to John Smith or his voicemail. DNS resolves host names (the machine named JohnSmith01) to an IP address (10.0.0.5). You're then connected to the host machine.

Historically, a drawback to DNS was the fact the DNS tables, which are consulted to resolve host names to IP addresses, were static. That is, somewhere someone (or something) had to make an entry into a DNS file. That information was then replicated out over the network or the whole Internet to other DNS servers to make sure everyone was up to date. The drawback was the manual administration requirement of DNS. That drawback has been mitigated to some extent in Win2K because the DNS model is now dynamic. That is, records in the DNS database are now updated automatically without operator intervention. (You may or may not know that in the good old days, someone somewhere had to enter DNS records manually into a DNS database. Talk about a bottleneck.)

Master Tip: One big assumption about dynamic DNS is that the DNS servers support the RFC (RFC 2136: Dynamic Updates in the Domain Name System or DNS UPDATE) that allows dynamic updates to DNS. Clearly, dynamic DNS is intended for homogeneous Win2K Server networks. Older DNS servers, such as some Unix-based machines, can't be dynamically updated.

DHCP is one of those things you either love or hate. Many people love DHCP because it simplifies the life of the IT admin. Not only does DHCP dish out IP addresses to client machines on your Win2K network, but it allows you to provide robust configurations as part of that dishin' process. For example, you can robustly configure a client machine with settings ranging from Time Offset to StreetTalk Directory Assistance (STDA) Servers. Granted, these are very specific settings (the first example deals with Greenwich Mean Time and the second deals with Banyan's directory service (see my April 2000 column for an education on directory services). Bottom line? You name it when it comes to TCP/IP-related client machine configurations in Win2K, and DHCP can do it.

So what's not to love? Several things. MCSEs have become disenchanted with DHCP because when it doesn't work, the user gets a notice early in the logon process communicating that no DHCP server was available. Not only can't the user log on at this point, but worse, the user typically can't work productively since they can't access network resources and perceive their lives to be doomed otherwise. In other words, the phrase, "No DHCP server available," is debilitating in the organization.

It has also been my experience that DHCP performs poorly in widely dispersed and subnetted enterprises. To be honest, sometimes it wasn't always apparent why DHCP does or doesn't perform well; but looking back to one incident at a large Pacific Northwest hospital, the IT manager took the fleet of clients machines back to static IP addresses. Perhaps you have your own negative experience with DHCP and can relate to this. If you don't use DHCP to serve IP addresses, you'll need to configure the IP address of your client machines manually.

Master Tip: I've used DHCP to pull an MCSE-quality rabbit out of my consulting hat on more than one occasion. For example, I was once confronted with a client situation whereby the client site was anticipating it would receive a range of real IP addresses from its ISP within a matter of days. Each PC was to then have a real IP address. Well, days grew into weeks. In order to get this site up and running, I created an internal network of IP addresses (using 10.0.0.x) and had DHCP assign the addresses to the workstations. The DHCP scope was defined to only lease the addresses for 72-hours. That way, with the addresses frequently renewing, when the real IP addresses finally arrived, rolling out those IP addresses would only be a function of creating a new DHCP scope with the real IP addresses and disabling the original DHCP scope. In plain English, the old 10.0.0.x IP addresses wouldn't be renewed and the new IP addresses would be leased out. Good stuff to say the least. More on DHCP scopes in a moment.

WINS is there if you need it and, likewise, not there if you don't. WINS is included in Win2K Server for legacy support reasons, the biggest of which is to support legacy environments such as older NT Server machines. WINS resolves NetBIOS names to machine addresses. As a mere earthling you can work with friendly machine names and actually find the machine (browsing through My Network Places is an example of this). WINS has a Madison Avenue-like feature whereby it's updated dynamically. That is, it updates its name resolution tables dynamically by listening to machines that advertise their respective NetBIOS names (as in "Hello! I'm ACCOUNTING01"). That dynamic updating of its name resolution tables is one of the cool features that undoubtedly was "borrowed" from WINS when the smart brains at Microsoft looked for ways to improve DNS!

Hands-on!

The easiest way to implement DNS and DHCP is to work from the Configure Your Server window (see Figure 1). This interface is meant to ease, if not hide, the complexities of installing services. It's conceptually similar to the SBS Console in Microsoft Small Business Server.

Figure 1. The fool-proof way to implement DNS and DHCP.

If you prefer the hard way or, more importantly, you want to drop down to a granular level to learn DNS and DHCP to pass your Win2K certification exams, you'll want to install these services from the Add/Remove Programs applet in Control Panel by following these steps.

1. Click the Start button on your desktop.
2. Select Settings and then Control Panel.
3. Double-click Add/Remove Programs
4. Click Add/Remove Windows Components in the left pane of the Add/Remove Programs dialog box.
5. Select Networking Services in the center of the Windows Components Wizard dialog box.
6. Click the Details button.
7. The Networking Services dialog box appears. Select the Domain Name System (DNS), Dynamic Host Configuration Protocol (DHCP) and Windows Internet Name Service (WINS) checkboxes as seen in Figure 2.

Figure 2. This is how you manually install DNS, DHCP, and WINS (via the subcomponents screen of Networking Services). Note the services are defined in the Description area of the dialog box.

This is how you would install WINS (as seen in Figure 1 above).

8. Click OK.
9. Click Next on the Windows Components Wizard screen.
10. When asked, supply the Win2K Server CD-ROM.
11. Click Finish when the Completing the Windows Components Wizard screen appears.
12. Close the Add/Remove Programs dialog box and the Control Panel. By the way, did you notice that you didn't need to reboot? It's a pleasant change from the old NT Server 4.0 days when installing every new service required a reboot.

Configuring each service (DNS, DHCP, or WINS) occurs via that service's respective Microsoft Management Console (MMC). I'll leave configuring DNS for another month-because it's such a huge topic!). Let's take a quick peek at configuring DHCP.

1. Launch the DHCP MMC from the Administrative Tools program group.
2. Right-click the Win2K server to display the secondary menu.
3. Select New Scope.
4. Click Next at the New Scope Wizard.
5. Provide a scope name (for example, "Headquarters--Scope 10.x.x.x) and a description and click Next.
6. Provide IP address range information. For example, the Start IP address might be 10.0.0.10 and the End IP address might be 10.0.0.100. Provide the Subnet mask information. Your screen should appear similar to Figure 3. Click Next.

Figure 3. DHCP scopes are configured via the New Scope Wizard. Here the IP address and Subnet Mask information is entered.

7. On the Add Exclusions screen, you typically provide a small range of IP addresses that aren't leased (say 10.0.0.20 to 10.0.0.25) in this example. These addresses are typically used for servers and network printers. Click Next.

Master Tip: No Self Service. A Win2K Server that acts as a DHCP server must have a static IP address. It can't serve itself a dynamic IP address. DHCP only leases IP addresses to clients (including other Win2K Servers) but not to itself. Note that the IP address of the server acting as the DHCP server is typically included in the exclusions (referenced in step 7 above).

8. You'll provide a lease duration on the Lease Duration screen. This is typically measured in days (eight days is the default). Practically speaking, this is how often the client machines will renew their IP addresses from the DHCP server. Click Next.
9. The Configure DHCP Options screen appears. Select Yes or No to configure options. Click Next.
10. Provide a router IP address on the Router (Default Gateway) address screen if you have a router or server acting as a default gateway on your network. Click Next.
11. Provide the Parent domain name and DNS server information. Click Next.
12. Provide WINS server information (name and IP address) if you have a WINS server on your network. Click Next.

Master Tip: The same Win2K Server machine can act as a DNS, DHCP, and WINS server.

13. On the Activate Scope screen, select Yes or No depending on whether you want to activate your new DHCP scope now or later. Click Next.
14. Click Finish on the Completing the New Scope Wizard screen. You have now configured a DHCP scope.

To configure DHCP scope properties (a good thing to practice to pass the demanding Win2K MCSE certification exams), right click on the scope folder in the right pane of the DHCP MMC and select Properties. The resulting screen, the Scope DHCP Server Properties, should look similar to Figure 4.

Figure 4. Learn the finer points of DHCP configurations by viewing the property sheet for the DHCP scope.

Another DHCP dialog box of interest is the Scope Options dialog box seen in Figure 5. Here you configure minute details of a DHCP scope. Again, very important on the Win2K MCSE certification exams.

Figure 5. Learn those Scope Option selections for both your real world use of Win2K Server and passing the Win2K MCSE certification exams.

Exam Implications

And speaking of exams (and without speaking outside of school or violating my Microsoft non-disclosure agreement), I can safely say that once again Microsoft has placed a premium on "stick-time," otherwise known as the long hours you pound the Win2K keyboard. Books are fine, and it never hurts to read columns such as this (for which I thank you), but there's nothing like stick time. For example, I recently took the beta test version of 70-216, Implementing and Administering a Microsoft Win2K Network Infrastructure exam, and discovered that-beyond the typical branch office and remote user story problems-over half of the exam was dedicated to DNS, DHCP, and WINS topics. While some of these questions were ivory tower planning questions, many more were hands-on dialog box selection-type questions. Your heard it here first.