Windows Server - Resolving DNS Names

Asked By SBN via WinServerKB.com on 21-May-07 04:31 AM
Hey I need some clarification pls correct me if im wrong. Heres the situation:


I have a DSL connection at home, our ISP gave me 1 class C routable IP
address, 2 class C DNS address and configure it on my XP Box. So with this
kind of setup when i try to search for a website i am using our ISP's 2 DNS
address that they gave mo to resolve the website and using the default
gateway (the default gateway that i used is the .1 of the class C routable IP
address given to me by my ISP)  to be able to connect to the internet, right?


But what is the difference if i configure my DSL configuration to a broadband
router (Linksys) and use it in a LAN with a win03 DNS server with AD, where
all XP Box is using the DNS server as their DNS.

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Herb Martin replied on 21-May-07 06:35 AM
The Linksys router will become the Default Gateway.


All INTERNAL DNS clients must use ONLY the internal DNS server (set)
supporting your AD Domain.

The Internal DNS Server usually will FORWARD (set it in the DNS MMC
properties for the Server, Forwarding tab) to the ISP or to your own gateway
or firewall DNS server.

Do not use your linsys router as a DHCP server unless you can arrange things
this way.
SBN via WinServerKB.com replied on 21-May-07 09:52 PM
- Ok so if i search for a certain site in our LAN using a clients web browser
the sequence will be CLIENT -> DNS SERVER -> DEFAULT GATEWAY -> INTERNET

- or will the client directly connect to the internet via the default gateway
if the LAN DNS Servers doesnt know the site?

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Herb Martin replied on 21-May-07 11:21 PM
IF the "Default Gateway" has a DNS server on it that can resolve the
Internet.

IF so, that is a very good way to do it.


Connect?  Yes, but lookup DNS directly?  NO, it must NOT use any
DNS server which cannot resolve ALL of the (Internal) records needed
by the client.


No, the JOB of the "internal DNS server (set)" used by the clients must
know OR be able to FIND all the records the client will EVER (legitimately)
need.

Usually by knowing the internal DNS records and forwarding for the Internet
records.


--
Herb Martin, MCSE, MVP
http://www.LearnQuick.Com
(phone on web site)
SBN via WinServerKB.com replied on 22-May-07 03:47 AM
Ok so basically the default gateway is just a node which is used to connect
you to the internet?
so in my pc if i will search for a site my computer will connect to the IP
address of a known default gateway configured to it, to be able to connect to
the internet...right? and then use the IP address of a known DNS servers also
configured to it, to be able find the site.

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Herb Martin replied on 22-May-07 05:19 AM
Yes.  It is a ROUTER to the Internet (in most cases).  As such that is all
it does, BUT many default gateways have other jobs, some are actually
(caching only) DNS servers which take care of the Internet portion of
Name Resolution when your INTERNAL DNS Servers forward to it.

Think of these as two separate jobs though, even if they happen to be on
the same machine.


Route to the internet would be a better way to say it.  You don't actually
connect TO the Internet, but rather ROUTE through it to connect to some
server or service on the Internet.

This is being picky with terminology but a lot of the mystery and difficulty
of networks can be removed if you are REALLY careful with your
terminology.


Right, the DNS resolves the name (of your desired site) to an IP address
and your machine uses that to "Route" the traffic (usually) through the
default gateway, and thus through the Internet to then reach that site you
were seeking.


--
Herb Martin, MCSE, MVP
http://www.LearnQuick.Com
(phone on web site)
SBN via WinServerKB.com replied on 23-May-07 01:09 AM
ah ok... Noted...

But in a LAN, like i in my case we have 2 Win03 DNS servers with AD and all
our computers are configured to use these servers as there primary and
secondary DNS servers but even without configuring these DNS servers on the
computers just the default gateway the computers can access the internet,
although our default gateway is a Linux box configured with our DSL
connection and is sharing internet access in our LAN. So does these internal
DNS servers will take part in resolving website addresses if place in a LAN?

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Herb Martin replied on 23-May-07 09:36 AM
As Preferred and Alternate -- technically Primary/Secondary have no
meaning for DNS CLIENTS doing resolution.


IN THEORY, but all access would be by IP address so that in practice
ordinary users couldn't make much practical use of it.


They MUST "take part" but they can do it by either doing the recursion
physically themselves, i.e., from the root DNS on the Internet down, or
by forwarding to another DNS server (set) to do this actualy resolution.

Generally forwarding is a better choice.

--
Herb Martin, MCSE, MVP
http://www.LearnQuick.Com
(phone on web site)
SBN via WinServerKB.com replied on 23-May-07 09:25 PM
Ok but if recursion or forwarding is not configured then basically they cant

Also what about this proxy server, if my web browser is set to use a proxy
then my computer will not use the assigned settings for internet access but
will directly connect to a proxy server...is it?

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Herb Martin replied on 23-May-07 09:55 PM
Yes, but one or both is practical always configured for an internal DNS
server.

Recursion is on by default.


That may be true, but only typically for Proxy aware applicatoins, like
(most) web browsers (and some other programs) -- although there are
also proxy "clients" that actually change the IP stack (wrap it in a proxy
client) function and thus work for (pretty much) everything.


--
Herb Martin, MCSE, MVP
http://www.LearnQuick.Com
(phone on web site)
SBN via WinServerKB.com replied on 24-May-07 03:36 AM
Is it good to have a proxy server and at the same time configure forwarding?

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Herb Martin replied on 24-May-07 04:09 AM
It depends on what all your particular Proxy does, how the clients are setup
to use it etc.

If there is no actual "proxy client" software but only programs like IE that
are SET to use the proxy then you almost always need the internal DNS
servers to forward (or recurse) to resolve the Internet.

--
Herb Martin, MCSE, MVP
http://www.LearnQuick.Com
(phone on web site)
SBN via WinServerKB.com replied on 24-May-07 09:40 PM
Everything is clear now.... thank you :)

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Herb Martin replied on 24-May-07 10:13 PM
Glad to help.

--
Herb Martin, MCSE, MVP
http://www.LearnQuick.Com
(phone on web site)