How do I... Configure DHCP for dynamic updates in Windows Server 2008?

For those companies considering an upgrade to Microsoft Windows Server 2008, it is very important to understand how DHCP and DNS work together to power Windows Server 2008. In this post, you will learn how to configure DHCP to dynamically collaborate with DNS and WINS in Windows Server 2008.

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.

This blog post is also available in the PDF format as a TechRepublic Download and as a TechRepublic Photo Gallery.

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

Scope Properties window

To access this menu and configure DHCP for dynamic updates:

1. Click Start | 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 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 dynamically Update DNS A and PTR records option, as we have done in Figure A, the DHCP server updates all A and PTR records. If you select the Discard A and PTR records when lease is deleted check box, when any client lease expires, the DNS entries expire and will be removed. Deselecting the box simply leaves your lookups there.

Configuring DDNS

To configure DDNS:

1. Click Start | 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 Secure only
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 B and Figure C.

Figure B

Secure Dynamic Updates

Figure C

Changing the zone type

If you select Active Directory-Integrated, you can choose Secure only from the 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

Adding the WINS IP Address

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

Adding the WINS-R IP address

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 more dynamic and easier to administer.