Hi,

since Windows 7 respectively Windows 2008R2 it has the ability to start a windows service with a trigger. Some Services, like dnscache, starts or stops on demand.

A customer had the problem that sometimes, after an automatic restart (on idle) of the DNS Client Service, Windows won’t register its name in DNS anymore. A manual register with
C:\> ipconfig /registerdns
was necessary each time.

The Workarounds by setting

• Enable the firewall rule “Network Discovery (LLMNR-UDP-In)”,  which means that Port UDP/5355 is not blocked
• And setting the DNS Client IdleTimeOut to 0xffffffff

  
  Windows Registry Editor Version 5.00
  
  [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters\Dnscache]
  "IdleTimeOut"=dword:ffffffff

had no effect.

I choose a pragmatic approach. To prevent the DNS Client (dnscache) from starting and stopping I removed the trigger from the service by the sc.exe command:

Query all triggers

C:\>sc qtriggerinfo dnscache
[SC] QueryServiceConfig2 SUCCESS

SERVICE_NAME: dnscache

        START SERVICE
          FIREWALL PORT EVENT          : b7569e07-8421-4ee0-ad10-86915afdad09 [PORT OPEN]
            DATA                       : 5355;UDP;

Remove the trigger

C:\>sc  triggerinfo dnscache delete
[SC] ChangeServiceConfig2 SUCCESS

To restore the default behaviour use

C:\> sc triggerinfo dnscache start/portopen/5355;UDP
[SC] ChangeServiceConfig2 SUCCESS

Michael