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

Recommended State:
  • 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:


  1. Guest says:

    It may be useful for your users to know that the XP DNS service is not in fact necessary to resolve dns lookups while using the internet. Disabling it simply removes XP's dns caching. Any machine less than a year old won't notice a speed difference but will gain some memory and cpu cycles.

    It is disabled on my system even now and I was able to dns to your site just fine.

    Thanks for an excellent service.

  2. snakefoot says:

    It is disabled on my system even now and I was able to dns to your site just fine.

    Have now been running with the DNS client disabled for 4 days(And yup DNS still works). Though I did notice that my applications suddenly wanted to do DNS lookups (ofcourse) and at the same time when some of my bandwidth was used (Not all) for downloading it had a greater impact on my Internet Browsing (Probably because it had to wait for the DNS replies as it was put behind the other network packets). I have enabled my service again, but I have also updated the description for the service.

    Thanks for an excellent service.

    Glad you like the page.

  3. AxL says:

    One question: when connecting to multiple users over a P2P network such as bittorrent, will the client do a DNS lookup on all peers? And if so, would it be just a single event or would the client do DNS lookups once every # minutes? If this is the case, wouldn't this constitute as a severe bandwidth killer?

  4. Snakefoot says:

    AxL wrote:
    will the P2P client do a DNS lookup on all peers?

    By default most P2P networks uses IP adresses directly and never performs DNS lookup of domain names.

  5. Michael Hodish says:

    Came across your dns utility while googling around today. I'm using Win 7 64 bit, and am tweaking things a little. Frankly, I am not sure that they latency of a dns lookup is a noticable factor, but, I am playing anyway.

    I have a hosts file for blocking badware and ads, and have set win in the registry to cache dns for some huge value, like 6000000 seconds... which is probably not the ideal way to use the cache.

    I was searching for some software to modify the hosts file, and found yours. It is close to what I think I seek, but I wonder if the following is practical, so that every site I hit just once doesn't wind up in hosts, makin git too big:

    do you know of a prog, or could yours be made to do this... to only add an ip to hosts if I have hit that ip at some user definable frequency... e.g. > 3 times in 24 hours.

    Also, I am not sure if win 7 doesn't already have some cleverness under the hood that renders this needless. What do you think?


    Mike Hodish

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