|Data type||Range||Default value|
|REG_DWORD||0 | 5 - 28 records||0|
Specifies the maximum number of A (host IP address) records that the DNS server is permitted to insert in the answer section of a response to an A record query (a query for an IP address). The value of this entry also influences the setting of the truncation bit. If the value of this entry is between 5 and 28, the truncation bit is not set on the response, even when the packet space is exceeded.
The value of AddressAnswerLimit is imposed upon A record queries only; it does not affect other types of queries.
|0||There is no limit on the number of A records in a response. If the response, including all A records, does not fit in a UDP DNS packet, the truncation bit is set.|
|5 - 28||The maximum permissible number of A records in a response. The truncation bit is not set, regardless of the size of the response.|
To change the value of this entry, use Dnscmd.exe, a tool included with the Windows 2000 Support Tools. The change is effective immediately; you do not have to restart the DNS server.
DNS reads its registry entries only when it starts. You can change entries while the DNS server is running by using the DNS console. If you change entries by editing the registry, the changes are not effective until you restart the DNS server.
This entry was designed to resolve a problem in DNS for Windows 95 (without service packs) in which DNS fails when it receives more than 28 A records in a response to an A query. This occurs infrequently and only when numerous servers are supporting a Web site. However, because the truncation bit is not set, limiting A records has the added benefit of preventing remote DNS servers from using TCP to retry these queries. DNS servers often use TCP to retry queries when they receive a response with the truncation bit set.
DNS does not add this entry to the registry. You can add it by editing the registry or by using a program that edits the registry, such as Dnscmd.exe.