Sams Teach Yourself MCSE Windows NT Server 4 in 14 Days
(Publisher: Macmillan Computer Publishing)
Author(s): David Schaer, et al
ISBN: 0672311283
Publication Date: 12/15/97

In the left pane, you should see the new zone you just added under the corresponding server. If you highlight this, you see current zone information in the right pane. You now are ready to add any subdomains you need. To add a subdomain, highlight the domain and then select New Domain under the DNS menu. Add any more subdomains you want in this manner. You also can add subdomains under other subdomains.

Now that you have created your zone and any subdomains, you are ready to start adding resource records to your domains. Resource records are the meat of your DNS database; the common types of resource records are summarized in Table 11.4.

You can add a record simply by selecting the domain to which you want to add it and selecting New Record from the DNS menu. This brings up the window shown in Figure 11.30.

Figure 11.30.  Adding a record to the DNS database.

Select the type of record you want to add in the Record Type section and enter the parameters in the Value section. For example, if you need the name ftp to point to IP address 192.168.0.141, simply add an A Record. Select A Record in the Record Type section. In the Value section, enter ftp in the Host Name field and enter the IP address in the Host IP Address field. Clicking OK should return you to the DNS Manager, where your new record should show up in the right pane (see Figure 11.31).

Figure 11.31.  Viewing a new record in the DNS database.

You also can administer Microsoft DNS Service the same way you would a traditional DNS by working with the files in the default installation path \systemroot\system32\dns.

11.5.2. Name Resolution with DNS

A client can make three types of queries to a DNS server:

•  Recursive queries: In a recursive query, a client requests information of a DNS server. The DNS server can reply with the IP address of the domain name requested or a message stating that the information could not be found. The DNS server cannot pass information along to another server.

•  Iterative query: In an iterative query, the DNS server can return the resolved IP address of a domain name or a referral to another DNS server with more information.

•  Inverse query: In an inverse query, the client requests that a computer name be found given a known IP address.

In Figure 11.32, a client computer in Chicago requests the IP address for the domain name http://www.hp.com. It does this using a recursive query, meaning that the information the client computer gets back will be either the IP address or an error message. The DNS server makes an iterative query to the DNS server whose zone of authority is the root-level domain names. The root DNS server refers the Chicago DNS server to the DNS server whose zone of authority is the top-level domain name com. This server then refers the Chicago server to another DNS server, whose zone of authority is hp. This server has the correct mapping in its database and returns the information to the Chicago DNS server, which in turn passes it back to the client.

Figure 11.32.  Querying a DNS server for domain name resolution.

11.5.3. Using WINS with DNS

DNS is a static database, which means that all information must be manually entered into it. WINS allows client computers to automatically register themselves with the WINS server so that their computer names can be resolved to their IP addresses. You can configure DNS and WINS to work together to provide quite a flexible name resolution scheme.

To do this, you simply must configure DNS to enable WINS lookup. This allows DNS to forward NetBIOS names to a WINS server for resolution. In DNS Manager, select the zone for which you want to enable WINS lookup and select Properties from the DNS menu. This brings up the property sheet shown in Figure 11.33.

Select the WINS Lookup tab and check the box next to Use WINS Resolution. In the WINS Servers section, enter the IP addresses of any WINS servers you want to use. You can also order them by priority.

Figure 11.33.  Enabling WINS lookup for a zone in DNS Manager.

11.5.4. Optimizing Domain Name Server

The amount of network traffic involved in using a domain name server (DNS) for name resolution consists of a client request and a DNS response, so it is of small impact on overall network traffic. However, traffic can be increased by the need for the DNS to do recursive lookups whether to another DNS or a WINS server.

Preventing recursive lookups altogether reduces network traffic but also decreases the effectiveness of the DNS for name resolution. Optimizing DNS traffic, therefore, should be aimed toward decreasing the number of recursive lookups while maintaining the effectiveness of DNS to provide for name resolution. This can be enhanced by pointing clients to the DNS that is most likely to have the requested address.

When a DNS does a recursive lookup, this information remains in the cache for 10 minutes. By increasing the time to live (TTL) of these cached entries, the results of recursive lookups remain in the cache longer, thereby preventing further lookups for those destinations that are accessed most frequently.