Helping people with computers... one answer at a time.
The DNS servers used on your computer are most likely specified by your ISP. I'll look at how to tell what they are and how to change them.
How do I find the domain name server on my PC?
The DNS (Domain Name System) server used by your PC provides the service that maps domain names (like "ask-leo.com") to IP addresses (like 220.127.116.11).
There are several different DNS servers that you could be using.
I'll look at how to quickly find out what your computer is configured to use and then, I'll show you a couple of approaches to setting different DNS servers.
In my opinion, the fastest and easiest way to determined what DNS server you're using is to use the Windows Command Prompt.
In Start, All Programs, Accessories, click Command prompt.
Microsoft Windows [Version 6.1.7601] Copyright (c) 2009 Microsoft Corporation. All rights reserved. C:\Users\LeoN>
(My example uses Windows 7, but this is essentially the same for XP and Vista as well.)
Type "ipconfig /all" followed by Enter:
C:\Users\LeoN>ipconfig /all Windows IP Configuration Host Name . . . . . . . . . . . . : NOTENQUAD Primary Dns Suffix . . . . . . . : Node Type . . . . . . . . . . . . : Hybrid IP Routing Enabled. . . . . . . . : No WINS Proxy Enabled. . . . . . . . : No Ethernet adapter Local Area Connection 2: Connection-specific DNS Suffix . : Description . . . . . . . . . . . : Marvell Yukon 88E8056 PCI-E Gigabit Ethernet Controller Physical Address. . . . . . . . . : 00-1D-60-2F-4B-39 DHCP Enabled. . . . . . . . . . . : No Autoconfiguration Enabled . . . . : Yes Link-local IPv6 Address . . . . . : fe80::b0c7:46c7:fe6:7355%12(Preferred) IPv4 Address. . . . . . . . . . . : 192.168.1.5(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.1.1 DHCPv6 IAID . . . . . . . . . . . : 301997408 DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-13-24-A8-36-00-1D-60-2F-44-E8 DNS Servers . . . . . . . . . . . : 192.168.1.2 18.104.22.168 NetBIOS over Tcpip. . . . . . . . : Enabled
There may be several networking adapters (particularly in Windows 7). Look for the one with a recognizable IPv4 address, most often starting with 192.168 - an IP address assigned by your router.
In the midst of the information there, you can see "DNS Servers" listed. Typically, there are multiple servers that provide backup access if one of them fails to respond.
In my case, I have a DNS server on my local LAN, as evidenced by the 192.168. IP address, and another as backup.
Yours will almost certainly be different.
Unless you override them, DNS settings are assigned by your ISP. When your router connects to the internet and asks your ISP for an IP address, the ISP's response also includes the IP addresses of one or more DNS servers.
When your computer then boots and asks your router for an IP address on your local network, the router will respond in either one of two ways:
It'll pass on the DNS information that it was given by your ISP.
It'll return its own IP address, meaning that the router itself will act as your DNS. This isn't uncommon and in fact, it can result in a small speed improvement. Your router passes on the DNS requests for anything that it hasn't already been asked about to the "real" DNS servers and returns the results more quickly if the DNS request has already seen and cached.
If you find that your computer's DNS is set to be your router's IP address, then to see what DNS server you're really using for requests that the router can't fulfill, you'll need to check the router's configuration; it should list the DNS that it's using. Exactly how you do that depends on your router, so check the documentation that came with it.
There are two basic approaches to overriding the DNS settings for your computer: configure the router to hand out DNS addresses that you specify, or configure your computer to ignore what the router tells it and use the DNS addresses that you specify.
Once again, exactly how you override the DNS settings used by your router will vary based on what router you have. In fact, not all routers have the ability to let you configure these settings. The advantage is that when configured in your router, the DNS servers will be used by all computers on your local network.
To change the DNS servers on your PC:
Windows 7: Right-click on the network icon in the notification area, and click Open Network and Sharing Center. Then, click Change adapter settings on the left. Right-click on the icon representing your network and click Properties.
Windows XP: In the Control Panel, click Network and Internet Connections, click Network Connections, then right-click the icon representing your network and click Properties.
You should see something similar to this:
Scroll down as needed and click Internet Protocol (TCP/IP) or Internet Protocol Version 4 (TCP/IPv4). Click the Properties button.
In the resulting dialog will be the setting that we care about:
When set to "Obtain DNS server address automatically", the computer will use the DNSs returned when it asks your router for an IP address.
When set to "Use the following DNS server addresses", you can specify the IP addresses of the DNS that you want to use.
To be clear, this is not normally a setting that you need to change. If you're not sure and things are working, then chances are that there's simply no need for a different setting.
Changing DNS servers is typically done for one of two reasons: filtering or speed.
OpenDNS provides DNS servers that are both fast and support filtering, if you set up a free account. OpenDNS's servers are:
Google also provides public DNS servers that are reasonably fast and free to use (and easy to remember). Google's servers are:
There are literally hundreds of DNS servers around the world, but those are two safe alternatives should your ISP's DNS servers not be up to the task or not be an option for some other reason.
Finally, if you want to really geek out and actually determine the DNS servers that would be fastest for your location, check out GRC's DNS Benchmark. It's not for the faint of heart, but it will measure the speed and other characteristics of many public DNS services and report which might be a more appropriate choice for you.