asked on

trying to understand the DNS set up !

I am just trying to understand the DNS setup and how its working ... I've a DNS server which is pointing to itself and has all the lookup records ... There must be some point where this DNS server has to talk to my ISP's DNS server to resolve requests ... Where can I find that DNS entry for ISP coz i check the router or the pix that has the connection out to the internet and it has no such command configured as "ip name-sever x.x.x.x" ... so am just trying to understand how is the DNS processing working ?

Lee W, MVP

Your Windows DNS server MAY be configured with forwarders (Forwarder settings). In which case, any domain name it cannot resolve will have the request forwarded to the server(s) defined in the setting. However, if there are no forwarders defined, then the resolution request is forwarded to the internet root servers as any other DNS server would.

nabeel92

ASKER

Ok ...I checked in the DNS server (forwarder) and I don't see anything configured .. I've attached 2 snapshots ... From what you mentioned, looks like all our DNS requests are resolved by the internet root servers ?
1.JPG
2.JPG

nabeel92

ASKER

Ok, this is what i noticed today ! I went to this other server which is configured as the secondary DNS server and in its forwarder, i found the ISP's DNS server I.P ...

Now, I have a primary DNS server (that I pasted the snapshots above) and is not configured with ISP's name server so i'm assuming it must be going out to the internet root sever ... The secondary DNS server is configured with ISP's DNS I.P ... So which 1 gets preference ... Are all the clients going via primary DNS (i.e. Internet root server ) or secondary DNS (ISP's DNS) ?

Attached is a snapshot of forwarder tab in my secondary DNS server
1.JPG

Chris Dent

> So which 1 gets preference ... Are all the clients going via primary DNS (i.e. Internet
> root server ) or secondary DNS (ISP's DNS) ?

Which one appears first in their TCP/IP configuration (ipconfig /all)? That one is used first, any later entries only if the first is busy (too slow to respond) or down.

The clients won't know what configuration is in place for the servers to get the answers, they just yell "hey, where is www.google.com?" and wait for a response.

If you're interested, you will find the list of root servers you query under "Root Hints". Those are used to start off the name resolution process, your server has to find it's way down the tree to get to a domain when using Root Hints. e.g.:

- Root knows where .com is
- .com knows where google.com is
- google.com knows where www.google.com is

When using Forwarders your server does what the client just did, yells at the forwarder and waits for an answer.

HTH

Chris

nabeel92

ASKER

so my primary one is basically forwarding to internet root servers ... and its cache is also set to default 1 hour ... wont that yeild poor performance ? if i change it to ISP and then change the cache time out to 24 hours ... ??

ASKER CERTIFIED SOLUTION

Chris Dent

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial