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TOPIC: question on DNS

question on DNS 9 years 6 months ago #22075

  • skylimit
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Hi all, I've recently read about DNS but have found it difficult answering this questions related to DNS. I'll be very grateful if someone could provide me with an answers. many thanks

1.How does a client find a name server at which to begin the search?


My answer:

Since a root server is an authority for the top level domain names, a client will begin
by contacting the root server which contains information on how to reach other servers.

Q2:How does a name server find another name servers that can answer questions when it cannot?

possible answer:
By checking to see if the client requesting the name resolution specified a recursive translation or iterative translation..... (something along these lines...)

any responses appreciated....
"...you are never too old to learn" anon
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Re: question on DNS 9 years 6 months ago #22082

  • Smurf
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1. The client must have the DNS Server configured in its TCP/IP Settings in order to query DNS. This determines which server it will ask.

2. A name server will find another name server by either;

- Have another DNS Server setup as a forwarder, typcially your ISP's DNS Server. This is better since the query may be contained in the ISP's DNS Servers cache and therefore it speeds the responses up.
- If no forwarder is there, then it will start to use the Root DNS Servers. The root server will then point to the next DNS Server along the FQDN, i.e. for www.microsoft.com it will go to the Root DNS Server, this will point to the .com server, which will then point to microsoft.com.

I think that the Recursive/Iteretive determines if the Client needs to start going to each DNS hop or if the DNS server does this on behalf of the client.

Cheers
Wayne Murphy
Firewall.cx Team Member
www.firewall.cx

Now working for a Security Company called Sec-1 Ltd in the UK, for any
Penetration Testing work visit www.sec-1.com or PM me for details.
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Re: question on DNS 9 years 6 months ago #22083

  • KiLLaBeE
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Just an add-on to answer 1:

When the ISP configures DHCP, the ISP can also provide the primary and secondary DNS servers' IP addresses and gateway's IP addresses, that way when a client first requests an IP address, it will receive an IP address along with the other information that it needs to surf the Net.

K
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Re: question on DNS 9 years 5 months ago #22142

  • skepticals
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When a resolver (client) issues an Iteration, the DNS server only responds with the best answer that it already knows. It consults the local data, if it does not find the answer it will send a referral. The referral will include the names and addresses of the name servers closest to the domain namin in the query. This will help the querier continue the resolution process.
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Re: question on DNS 9 years 5 months ago #22173

  • skylimit
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thanks alot guys...
"...you are never too old to learn" anon
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