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2) No PCs talk to their defined DNS servers. DNS servers will do any recursive queries needed if configured, and that could mean root hints or predefined forwarders. Clients never do recursive queries themselves.
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2) No PCs talk to their defined DNS servers. DNS servers will do any recursive queries needed if configured, and that could mean root hints or predefined forwarders. Clients never do recursive queries themselves.

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3) too broad. Can't answer.
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Thanks i meant 401 unknown error if one open web site
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Thanks i meant 401 unknown error if one open web site

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You need to look at logs. One million and one things can cause that.
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You need to look at logs. One million and one things can cause that.

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i wanted to know following:<br />
<br />
1) how a user in domain joined workstation authenticates &nbsp;<br />
<br />
like LDAP protocol to contact DC how it works and where DNS comes in picture , also how user authenticates and his login works<br />
<br />
2) in normal situation when we browse internet from OUR PC, does it contacts root hints &nbsp;and what is root zone ? does DC has root hints file?<br />
<br />
3) if a website is not working, what all we need to check on IIS part?
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i wanted to know following:

1) how a user in domain joined workstation authenticates  

like LDAP protocol to contact DC how it works and where DNS comes in picture , also how user authenticates and his login works

2) in normal situation when we browse internet from OUR PC, does it contacts root hints  and what is root zone ? does DC has root hints file?

3) if a website is not working, what all we need to check on IIS part?

ACTIVE DIRECTORY, IIS

The Domain Name System (DNS) is a hierarchical, globally distributed system responsible for associating the name of a computer, service or other resource into an IP address for connecting to the Internet or a private network. Most prominently, it translates domain names to the numerical IP addresses needed for the purpose of computer services and devices worldwide.

Active Directory (AD) is a Microsoft brand for identity-related capabilities. In the on-premises world, Windows Server AD provides a set of identity capabilities and services, and is hugely popular (88% of Fortune 1000 and 95% of enterprises use AD). This topic includes all things Active Directory including DNS, Group Policy, DFS, troubleshooting, ADFS, and all other topics under the Microsoft AD and identity umbrella.

Active Directory

IIS is Internet Information Services, the web server included with Windows Server operating systems. All current versions are built on a modular architecture; modules can be added or removed individually so that those required for specific functionality are installed. The full installation of IIS includes HTTP, security, content, compression, caching, logging and diagnostics.