DNS Client


The DNS Client acts like a local DNS server, and is used whenever an application requires to resolve a Domain Name System (DNS) name.

If an application wants to connect to www.google.com, then it requests the DNS client for it to convert it to an IP address. If the DNS client doesn’t recognize the domain it passes the request to the network DNS Server (Port 53), but caches the reply for later use by the same or other applications and thus increases the speed of future DNS lookups and causes less load on the network DNS Server.

When using WinXP to logon to a domain one should register the domain server’s IP as the primary DNS Server. If this is not done the login to the domain will be very slow.

When using Win2k/WinXP to logon to a WinNT4 domain one should enable Netbios over TCP/IP for the Internet Protocol in network properties on Win2k/WinXP as the WinNT4 domain doesn’t use DNS.

Note if using a large HOSTS file to ban ads, then it will lead to slow performance when having the DNS Client enabled. To avoid the slowdown, then one either has to disable the DNS Client or avoid using a large HOSTS file.

Note in Windows XP this service keeps the same UDP connection open to make all DNS requests. In Windows 2000 the service opens/closes a UDP connection for each request. To make XP behave like Windows 2000 use this DWORD registry key:

[HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \Dnscache \Parameters]
MaxCachedSockets = 0

Note if having disabled this service, and then try to repair a network connection, one will get the following error message:

The following steps of the repair operation failed: Purging the DNS Resolver Cache. Please contact your network administrator or ISP.

More Info MS KB913631

Related Configure how long to cache negative DNS replies
Related Microsoft TCP/IP Version 6 (IPv6) can cause slow DNS
Related Configure the host name resolution order
Related Use HOSTS file to ban ads and speedup DNS lookups

More Info MS KB286834
More Info MS KB264539
More Info MS KB268674
More Info MS KB245437
More Info MS KB246804
More Info MS KB294832
More Info MS KB320760

  • Automatic, to minimize network traffic for the cost of memory.
  • Disabled, if not wanting to have DNS caching and want every application to do their own DNS lookup.
Default State:
  • Win8: Automatic (Trigger Start - FIREWALL PORT EVENT)
  • Win7/Vista/WinXP/Win2k3/Win2k: Automatic
Process Name: