A Question About Dns Servers

[doctormann]

I'm sure that there's a definitive answer to this question but I haven't been able to find it.

I can set preferences for DNS servers either on my D-Link Router or in the Properties of my internet connection on my PC. Which takes precedence? Is one method preferred over the other?

If I set the DNS preferences on the PC to 'point' to the default gateway on the router are the DNS settings on the router then used? Is this a sensible thing to do?

I'm still running XP Pro on my dinosaur of a PC and I have the system set up to give static addresses on my LAN - two machines - for purposes of port forwarding. DHCP is disabled. I don't know if this makes any difference with regard to how the DNS preferences should be set.

I normally use a combination of the Google 8.8.8.8 server and one from my ISP (ToT).

Help please.

DM

[Supernova]

I can set preferences for DNS servers either on my D-Link Router or in the Properties of my internet connection on my PC. Which takes precedence? Is one method preferred over the other?

DNS specified by the operating system takes precedence. As to which method is preferred, is a subject of much debate. I tend leave my router DNS settings alone, and configure DNS from within the operating system (e.g. Windows network adapter settings).

If I set the DNS preferences on the PC to 'point' to the default gateway on the router are the DNS settings on the router then used?

Yes.

However, I've always held the belief that specifying the actual DNS server address in Windows (instead of having it point to the default gateway) to be more "efficient" since the OS does not need to query the router for DNS numbers. To ensure I have all bases covered, I always add the default gateway to the bottom of the list of DNS server addresses.

I'm still running XP Pro on my dinosaur of a PC and I have the system set up to give static addresses on my LAN - two machines - for purposes of port forwarding. DHCP is disabled. I don't know if this makes any difference with regard to how the DNS preferences should be set.

DHCP on or off, shouldn't make any difference.

[rakman]

I can set preferences for DNS servers either on my D-Link Router or in the Properties of my internet connection on my PC. Which takes precedence? Is one method preferred over the other?

DNS specified by the operating system takes precedence. As to which method is preferred, is a subject of much debate. I tend leave my router DNS settings alone, and configure DNS from within the operating system (e.g. Windows network adapter settings).

If I set the DNS preferences on the PC to 'point' to the default gateway on the router are the DNS settings on the router then used?

Yes.

However, I've always held the belief that specifying the actual DNS server address in Windows (instead of having it point to the default gateway) to be more "efficient" since the OS does not need to query the router for DNS numbers. To ensure I have all bases covered, I always add the default gateway to the bottom of the list of DNS server addresses.

I'm still running XP Pro on my dinosaur of a PC and I have the system set up to give static addresses on my LAN - two machines - for purposes of port forwarding. DHCP is disabled. I don't know if this makes any difference with regard to how the DNS preferences should be set.

DHCP on or off, shouldn't make any difference.

1) If you use DHCP for IP and DNS, the DNS in the PC network settings is set to the gateway of the router and will query the router, who will query the ISP DNS servers, who either has the DNS entry or should jump to the Root DNS servers, if the ISP DNS server(s) are Root DNS server aware. Otherwise, its a long journey for a simple DNS request.

If the router uses DHCP from the ISP (internet provider) then the router DNS is set by the ISP. unless overridden manually.

If you use static IP in the PC on the router interior network, you'll need to manually set DNS settings, otherwise, the PC won't know who to query and won't resolve any web address (except by IP).

Static or DHCP in the PC can be set to any DNS server. This is a neat tool for determining the quickest DNS server to use: http://www.codeproject.com/KB/IP/DNSTester.aspx

2) yes, and a good idea to include the router as a "last resort" query. The ISP usually gives 2 DNS servers to query, which are usually DNS server farms. Google's 8.8.8.8 is a DNS server farm.

3) You'll need to manually set DNS in each PC. If DHCP or static IP settings use the same DNS server settings, then no difference is encountered. However, you might be able to detect a slight speed up if you set the IP address and name of common sites in your %Windir%\system32\driver\etc\hosts file. Hosts file is read first, then queries by DNS. The only problem there is if a site changes IP, you won't connect until you change or delete the hosts file entry for that site.

[Guest]

I would think that it's best to let the router to work as DNS server (and proxy). At least in the case that you have multiple computers which are accessing the same services on the internet.

I'm not 100% sure, but this is what I think happens. When you (your browser) send an DNS query it's fist checked on your computer local dns-cache.

If not there, the query is send to defined dns-server address to the router. From there to the ISP or otherwise defined dns-server.. and to the domain name own servers .. and the way back. This will take time from 20 to 500ms, depending of the connection and how far and fast is the dns-server.

For the same computer, the resolved address is already on the computer local cache and it will get it really fast. Or it can get it from the local dns.

For the other computers, the dns query is sent only to the local router (1-15ms)

Just did an test with the same query twice using CAT CDMA EVDO network

1) First query (www.fi) when DNS information is fetched from the bottom of the internet

real 0m0.485s

Time was 485ms

2) Second query (www.fi) from router dns-server

real 0m0.012s

Time was 12ms

Today's websites could have tens of DNS addresses offered by one single page view. Good dns does make the difference.

-Pekka

[doctormann]

Thanks to those who replied. I'm a little clearer on this matter now.

DM