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Okay maybe not, but i am a bit confused, The address of the DNS server is obtained by the modem (via DHCP) so why does it matter if we change the DNS address in windows? Is operating system's configuration given priority over the Modem's configuration? And does it this configuration really works faster then the one provided by ISP or it's just a placebo?

Puru
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5 Answers5

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Yes, the DNS is a service of choice, you can choose the DNS you want on end user, you can even create a static DNS on your host.

ebilcari
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The answer is yes: your OS will use whatever DNS servers you tell it to. The modem is given some DNS servers by the ISP, and it will then serve them to its clients via DHCP, but the clients are free to ignore tham and use alternative servers if they wish.

Flup
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In a word, yes – the OS setting is given priority. Your system would get the DNS server from its DHCP server (aka your modem) which in turn gets its DNS setting upstream from your provider. But if you force a value in at the modem and let your computer pick it up from there, then that would be the DNS server. And if you force the value in at your computer, that is the value that is used regardless of what your modem or upstream provider has set.

grawity
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Silly boys...

Google DNS servers are listed in the official Internic database hosted at ICAAN. The Google DNS servers are listed as:

ns1.google.com

ns2.google.com

ns3.google.com

ns4.google.com

These servers have one IP address each, although there may be load balancers spreading the requests to a farm.

When a client needs an IP address for the google search engine, it will ask the bind server which is configured into the network config for that workstation. If this bind server does not know google's IP (or range of IP's) then it may inquire from any of the 4 Google bind servers. It will then cache the answer should anyone else need to know Google's IP so that Google's bind servers do not get hit every time someone needs the IP.

This is the way the bind system is designed. As a distributed lookup system.

Marianna
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In your PC you have 3 options:

  1. Configure a static IP and provide the DNS server(s) to use.
  2. Set your PC to use DHCP.
  3. Set your PC to use DHCP, but also provide the DNS server(s) to use.

In scenario 2 your PC gets all he needs (IP address, network mask, router, DNS server(s)) from the router. In scenario 2 your PC gets most he needs (IP address, network mask, router) from the router, but you override the DNS server(s) to use. The router might still tell the PC which DNS server(s) he can use, but the PC will ignore that and use the ones you configured.

How does your router know the DNS server(s) from your ISP? Because your router uses DHCP to talk to your ISP and get it's IP address, ... and the DNS server(s). The ISP will tell your router to use his own DNS server(s). As with PCs some routers allow providing alternate DNS server(s) as override.

If you change the DNS server(s) at your PC, this will only affect this PC, no other PC and not the router. If you change the DNS server(s) at your router this will affect the router itself and all PCs that learn the DNS server(s) from the router.

You asked if there is any advantage when using Google DNS. I read about three reasons:

  1. Google DNS is faster
  2. Google DNS is more secure
  3. Google DNS comes without censoring

I am not sure if Google DNS really is faster. My hope would be that a good provider knows what he is doing and that you profit from the short way from your router to your ISP's DNS server, a way that is totally under control of the ISP and could be optimized. If you want to check which DNS is fastest, you can use namebench.
By the way, I doubt that speed is relevant. DNS resolving is taking milliseconds. And if the PC once resolved a name to an IP address, he caches this information for some time. So a second DNS resolve request only a few seconds later will not result in any packet being sent to any DNS server. You can see the list of cached DNS names if you want to: start cmd.exe and there enter ipconfig /displaydns).

Second reason is a more secure DNS, but also this depends on your ISP and the DNS server they are using.

The third reason probably is a good one. If you live in a country with censorship and/or DNS filtering then some DNS names might not be blacklisted and not be resolved by your ISP. Your ISP might not have a choice because of legal reasons. In this case a Google DNS that is (or claims to be) uncensored/unfiltered is a good alternative to get full internet access. Of course this might not work in all countries because the ISPs might also be obliged to filter out traffic from/to Google DNS.

Werner Henze
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