Modify EDNS0 configuration

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

To modify EDNS0 configuration

Open Registry Editor.

Caution
- Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on the computer. You can also use the Last Known Good Configuration startup option if you encounter problems after manual changes have been applied.
In Registry Editor, navigate to the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Parameters
Add the following DWORD entry:

EDNSCacheTimeout
To change the cache timeout, type a value in seconds between 3600 (1 hour) and 15724800 (182 days).
In the same registry subkey (Parameters), add the following DWORD entry:

EnableEDNSProbes
To configure the DNS server to include an OPT resource record only in response to EDNS0 requests containing OPT resource records, type 0x1 (DWORD).
Restart DNS server.

Notes

To perform this procedure, you must be a member of the Administrators group on the local computer, or you must have been delegated the appropriate authority. If the computer is joined to a domain, members of the Domain Admins group might be able to perform this procedure. As a security best practice, consider using Run as to perform this procedure.
To open Registry Editor, click Start, click Run, type regedit, and then click OK.
The value of the registry key EDNSCacheTimeout determines how long the DNS server will keep information about the EDNS versions supported by other DNS servers that have responded to a query with a OPT resource record.

Open Command Prompt.
Type one of the following:
- dnscmdServerName**/Config/EDNSCacheTimeout**Value
- dnscmdServerName**/Config/EnableEDNSProbes**Value

Value	Description
dnscmd	Specifies the name of the command-line program.
ServerName	Required. Specifies the DNS host name of the DNS server. You can also type the IP address of the DNS server. To specify the DNS server on the local computer, you can also type a period (.).
/Config	Required. Specifies the command to configure the DNS server.
/EDNSCacheTimeout	Required. Specifies the length of time the DNS server remembers the EDNS parameters remote servers report.
/EnableEdnsProbes	Required. Specifies whether or not the DNS server probes other DNS servers to determine if they support EDNS.
Value	Required. For /EDNSCacheTimeout, type a value in between 3600 (1 hour) and 15724800 (182 days). For /EnableEDNSProbes, type 1 to configure the DNS server to probe other DNS servers and determine if they support EDNS. Type 0 to configure the DNS server to not probe remote servers for EDNS support. If you type 0, the DNS server will continue to use EDNS if other servers request it.

Notes

To perform this procedure, you must be a member of the Administrators group on the local computer, or you must have been delegated the appropriate authority. If the computer is joined to a domain, members of the Domain Admins group might be able to perform this procedure. As a security best practice, consider using Run as to perform this procedure.
To open a command prompt, click Start, point to All programs, point to Accessories, and then click Command prompt.
This procedure requires the Dnscmd Windows support tool. For information about installing Windows support tools, see Related Topics.
To view the complete syntax for this command, at a command prompt, type:

dnscmd /Config help
For information about the current registry setting, type one of the following:
- dnscmd /Info /EDNSCacheTimeout
- dnscmd /Info /EnableEDNSProbes

Format	Meaning
Italic	Information that the user must supply
Bold	Elements that the user must type exactly as shown
Ellipsis (...)	Parameter that can be repeated several times in a command line
Between brackets ([])	Optional items
Between braces ({}); choices separated by pipe (\|). Example: {even\|odd}	Set of choices from which the user must choose only one
`Courier font`	Code or program output

Your server might function differently based on the version and edition of the operating system that is installed, your account permissions, and your menu settings. For more information, see Viewing Help on the Web.