What is DNS?
In most cases, two DNS servers, one primary and one secondary, are automatically configured on your router and / or computer when they connect to your ISP through DHCP. You can configure two DNS servers in case one of them fails, after which the device will resort to the use of the secondary server.
While many DNS servers are operated by ISP and are intended to be used only by their clients, several public access servers are also available. See our list of public and free DNS Servers for an updated list and How can I change the DNS servers? if you need help to make the change
Some DNS servers can provide faster access times than others, but they depend only on the time it takes your device to reach the DNS server. If your ISP’s DNS servers are closer than Google’s, for example, you may find that addresses are resolved more quickly using the default servers of your ISP than with a third-party server.
If you have network problems where it seems that no website will load, there may be a problem with the DNS server. If the DNS server can not find the correct IP address that is associated with the hostname it enters, the website will not load. Again, this is because computers communicate through IP addresses and not host names: the computer does not know what it is trying to reach unless it can use an IP address.
The DNS server configuration “closest” to the device are those that apply to it. For example, although your ISP might use a set of DNS servers that apply to all routers connected to it, your router might use a different set that would apply DNS server configuration to all devices connected to the router. However, a computer connected to the router can use its own DNS server configuration to override those established by both the router and the ISP; The same can be said about tablets, telephones, etc.
We explained earlier how malicious programs can take control of your DNS server configuration and override them with servers that redirect requests from your website to another location. While this is definitely something that scammers can do, it is also a feature found in some DNS services like OpenDNS, but it is used in a good way.
For example, OpenDNS can redirect adult websites, betting websites, social networking websites and more to a “Blocked” page, but you have full control over redirects.