For those companies upgrading to Windows 2000, and especially those using Active Directory, it is very important to understand how DHCP and DNS work together to power Windows 2000. In this article, you will learn how to configure DHCP to dynamically collaborate with DNS and WINS in Win2K.

DNS gets dynamic
Under Windows NT, DNS was static and had to be manually altered to make changes. With the advent of Windows 2000, many administrators were elated to hear that it contained a new feature called Dynamic DNS (DDNS). Basically, DDNS, in conjunction with DHCP and Active Directory, can provide secure dynamic updates for your A and PTR records in DNS.

For example, a client machine receives an IP address from DHCP and then DHCP automatically (as long as it is configured to support DDNS) passes along the host information for that machine to the DNS service. This feature alone can save an administrator a lot of valuable time.

Configuring DHCP for dynamic updates
As you can see by the Properties sheet shown in Figure A, you have a number of options to consider when configuring DHCP for dynamic updates.

Figure A

To access this menu and configure DHCP for dynamic updates:

  1. Click Start | Programs | Administrative Tools and select DHCP.
  2. Right-click on the DHCP scope you want to configure and click Properties.
  3. Click the DNS tab.
  4. Configure your settings.
  5. Click OK.

The default in Windows 2000 is for a DHCP client to update A (host name) records and have the DHCP server update the PTR records. If you select the Always Update DNS option, as we have done in Figure A, the DHCP server updates all A and PTR records. If you select the Discard Forward Lookups When Lease Expires check box, when any client lease expires, the DNS entries expire and will be removed. Deselecting the box simply leaves your lookups there.

Finally, selecting the Enable Updates For DNS Clients That Do Not Support Dynamic Update check box causes the DHCP server to always update the PTR record of the client. If you want the A record to be registered, you will need to know the DNS domain name. To perform this function, set your DNS domain name in the DHCP Scope Options, as shown in Figure B.

Figure B

Configuring DDNS
To configure DDNS:

  1. Click Start | Programs | Administrative Tools and select DNS.
  2. Right-click on the zone you want to configure and select Properties.
  3. In the General tab, choose Yes or No to Allow Dynamic Updates. If AD is installed, you will have an additional option of Only Secure Updates.
  4. Click OK to close the Properties screen.

When configuring DDNS, you can pause the DNS service and change the zone type, as shown in Figure C.

Figure C

If you select Active Directory-Integrated, you can choose Only Secure Updates from the Allow Dynamic Updates drop-down list. If AD is not running, your choice is simply Yes or No to allow dynamic updates.

Configuring WINS and WINS-R
Now we can spice things up a little more by introducing WINS and WINS-R into the mix. For the uninitiated, WINS resolves computer names to IP addresses (similar to DNS), and WINS-R provides reverse DNS lookups.

In addition to configuring DDNS, you can configure your DNS server to use WINS for name resolution. To perform this function, open the DNS console, right-click on your forward lookup zone, and select Properties (Figure D).

Figure D

Choose the WINS tab and enter the IP address of your WINS server. To configure WINS-R, follow the same steps but right-click and choose Properties on the reverse lookup zone (Figure E).

Figure E

Final word
You now know how to properly configure DDNS to dynamically update your DNS records and how dynamic updates will save you from maintaining static mappings. You’ve also learned how WINS can be integrated into this equation and how DHCP and DNS collaborate to make Windows 2000 more dynamic and easier to administer.

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