question in dns and bind
 

hi ,
i want to ask a question in dns


if i configured forwarder in my bind config ,

assume that client request a query that not in my server and not in the forwarder ,

wil the client ask the root dns servers ???


i mean when we ask the root servers ???
as i remember they are 13 servers




wish to clarify


regards

This heavily depends on the configuration of the server. If you enable recursive queries the dns server will do the whole query starting from the root server if not found in its cache.
Considering your case I doubt that the client will ask the root server. It sure will only do so if it has one of the root servers configured as its dns server. Also I somewhere a long time ago read that for instance ms clients dont do recursive dns queries so they would not query any further.
As for linux clients you can just try it out. Add on of the root servers to your /etc/resolv.conf and dig google.com

hi thansk alot ,
lets be more accurate

now im server DNS1

i configured my self with bind and clients put my ip in their network card for dns

i configured forwarders in my config ,



now ,


when client request ass www.linuxquestions.org

the client will ask my internal cache of dns , and assume not found

then it will ask forwarders that i configured

my question is
assume the forwarder didnt find an anser for the query ,

will DNS1 server go to ask global 13 root server and give answer to that client ??

i mean when the dns server go to ask the root hints ?
it it always ?? or when it cant find it from locally anf forwarders


with to clarify ,


with my best regards

If the forwarder can not provide an answer the dns server will ask the root servers. That is what I'm know to be a recursive query. This is if a server can not answer the query of the client by him self he will ask the root servers and follow the trail. Clients seldomly make recursive calls.

Just keep in mind that there are options for bind that allow or deny recursive queries completely or based on ip address.

hi , thanks alot ,

but agian

plz imagine my scenario



client(a)-------------dns----------------->forwarder dns2
|
|
|
root hints


now client 1 requested www.linuxquestions.org

nut not found neither on dns no nor client cache
now ,

the dns will query request to forwarder , it will ask forwarder dns2

Question # 1:
will dns ask dns2 recursive or iterative query ?? "" now im talking about when it call the forwarder "


Question # 2

assume dns2 forwarder didnt find the answer ,

will dns ask the root hints ??? or just tell client that he dont know ???!!!


question # 3

i read about queries that comne from clients " i mean pcs " i found many of them send recursive query not itertive ,
wish to make sure




with my best regards

This all heavily depends on the configuration of both clients and dns server. I'd say you can configure the server to just tell the client I don't know if it can't resolve it through forwarders or even by itself. But as soon as the server askes on of the root server he will in most cases do all the work till it can be resolved or the appropiate other dns server tells him the query can't be resolved.

On clients I only know that WinXP machines only do iterative queries. Per default dunno if there is an option.

Guess you have to see for yourself what goes on for your use case and clients.

hi , thanks alot


but i have question

why we need to do NS record ??

i mean wts the benefit of that ??
i mean that the only server is the primary server for NS record , why we may need to ad more servers as ns record ???


regards

Maybe this will shed some more lights on the overall concept of domain name service
http://dnsfunda.blogspot.de/