Configuring DNS Servers and Clients in Visual Studio .NET

Encoding Code 128 in Visual Studio .NET Configuring DNS Servers and Clients

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When configured as shown in Figure 4-13, a DNS client running Windows 2000, Windows XP, or Windows Server 2003 can register resource records in DNS according to its three distinct names and sets of IP addresses, as shown in Table 4-4.

Table 4-4

IP Addresses 10.1.1.11, 10.2.2.22 Description The full computer name. The com puter registers A and PTR resource records for all configured IP addresses under this name in the exam ple.microsoft.com zone. The connection-specific DNS name for LAN connection 1, which registers A and PTR resource records for IP address 10.1.1.11 in the public.exam ple.microsoft.com zone. The connection-specific DNS name for LAN connection 2, which registers A and PTR resource records for IP address 10.2.2.22 in the backup.exam ple.microsoft.com zone.

After consulting its cache, the DNS Client service next attempts name resolution through its preferred connection, which is the first connection listed in the output of the Ipconfig command. Through this connection, the resolver (DNS client) queries the address designated as that connection s preferred DNS server. Although each network adapter can be configured with a unique list of DNS servers, it s perfectly valid to configure each network adapter identically to make DNS resolution more predictable. To help DNS clients resolve names when initial query attempts fail, each connection configured on the DNS client computer can contain a list of DNS servers to contact. As shown in Figure 4-14, you can configure a preferred server and a single alternate server for any connection in that connection s Internet Protocol (TCP/IP) Properties dialog box.

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Figure 4-14

However, for a given connection, you can create a DNS server list of any length in the connection s Advanced TCP/IP Settings dialog box. In this list, the first entry is treated as the preferred server and the remaining alternate servers are queried together. When resolving names, the DNS Client service queries the DNS servers in the following order: 1. The DNS Client service sends the query to the first server on the preferred adapter s list of DNS servers and waits 1 second for a response. 2. If the DNS Client service does not receive a response from the first server within 1 second, it sends the query to the first DNS servers on all adapters that are still under consideration and waits 2 seconds for a response. 3. If the DNS Client service does not receive a response from any server within 2 sec onds, the resolver sends the query to all DNS servers on all adapters that are still under consideration and waits another 2 seconds for a response. 4. If the DNS Client service still does not receive a response from any server, it sends the query to all DNS servers on all adapters that are still under consideration and waits 4 seconds for a response. 5. If it still does not receive a response from any server, the resolver sends the query to all DNS servers on all adapters that are still under consideration and waits 8 sec onds for a response.

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If the DNS Client service receives a positive response, it stops querying for the name, adds the response to the cache, and returns the response to the client. If the DNS Client service has not received a response from any server by the end of the 8-second time period, the resolver responds with a time-out.

The DNS Client service attaches DNS suffixes to any name that you enter in a query when either of the following conditions is true:

The name is a single-label unqualified name. The name is a multiple-label unqualified name, and the DNS Client service did not resolve it as an FQDN.

Default DNS Suffix Searches By default, the DNS Client service first attaches the pri mary domain suffix of the local computer to the unqualified name. If the query fails to resolve this name, the DNS Client service then adds any connection-specific suffix that you have assigned to a network adapter. Finally, if these queries are also unsuccessful, the DNS Client service adds the parent suffix of the primary DNS suffix. For example, suppose the full computer name of a multihomed computer is computer1.domain1.microsoft.com. The network adapters on Computer1 have been assigned the connection-specific suffixes subnet1.domain1.microsoft.com and subnet2.domain1.microsoft.com, respectively. If on this same computer you type computer2 into the Address text box in Internet Explorer and then press Enter, the local DNS Client service first tries to resolve the name Computer2 by performing a query for the name computer2.domain1.microsoft.com. If this query is unsuccessful, the DNS Client service queries for the names computer2.subnet1.domain1.microsoft.com and computer2.subnet2.domain1.microsoft.com. If this query does not succeed in resolving the name, the DNS Client service queries for the name computer2.microsoft.com.