DNSTermsConcepts[1]

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ESO Readiness & Sustained Education

© 20 June 2002

Course OverviewCourse Overview

Understanding and Troubleshooting DNS in Understanding and Troubleshooting DNS in Windows® 2000Windows® 2000

This course explains DNS name resolution and discusses namespace planning. Course modules provide in-depth analysis of best practices for installing, maintaining, and troubleshooting DNS services in Windows® 2000 networking and Active Directory environments. Screen-capture demonstrations illustrate key administrative, configuration, and troubleshooting tasks.

Presented by Mark Simos, Bill NoonanCourse Length 4 hoursDemonstrations 5 – see Modules 2 & 4Lab sessions None


See Notes for Slide 2

Your PresentersYour Presenters

Bill Noonan Microsoft® Enterprise Support Sustained Education Team

Mark Simos Microsoft® Enterprise Support Directory Services Team



Course PrerequisitesCourse Prerequisites

Before starting this course, you should: Be able to explain the concepts of and perform

administrative tasks for: Windows® 2000 Active Directory. Windows® 2000 Networking.



Learning ObjectivesLearning Objectives

Upon completion of this course you will be able to: Describe the role of DNS in the Windows® 2000 networking

and Active Directory environments Configure both client- and server-side DNS options Describe the DNS Name Resolution process List and Discuss Server-side functions including Zone

Transfer and Dynamic Registration of resource records. Discuss and illustrate DNS Namespace planning

considerations Describe common DNS problem scenarios and apply best

practices for troubleshooting DNS using available tools.



Course ModulesCourse Modules

Module 1. Concepts and Terminology 1.1. Overview and History 1.2. Zones, Records, and Delegation 1.3. Queries

Module 2. Processes 2.1. Client Configuration 2.2. Name Query Process 2.3. Server-side Processes 2.4. Dynamic Updates

Module 3. Case Studies Module 4. Best Practices and Troubleshooting



Course FormatCourse Format

Complete Digital Training Package Video presentations with slides and on-screen notes. Reference Library resources:

► Downloadable presentation slides and notes.► White papers and Knowledge Base articles.► Related web sites

Training materials are available online and on CD.Materials may be used for self-study, instructor-led delivery, and research

Intended Audience Microsoft® Support Professionals Microsoft® Consultants Network administrators and maintenance personnel


Let’s Get Started!Let’s Get Started!

Module 1 Section 1

Concepts and Terminology:Overview and History

To review materials in this module:To review materials in this module:1. Click Play. <OR>

2. Select a slide from the Index.


Module 1Module 1

DNS Concepts and TerminologyDNS Concepts and Terminology

This module defines key DNS concepts and terms to establish or reinforce knowledge of DNS functions.

The first section discusses the history of DNS, defines commonly used DNS terms, and explains concepts such as namespace, naming conventions, and record storage.

Presented by Mark Simos, Bill NoonanSession Length 20 minutesDemonstrations NoneLab sessions None


Discussion TopicsDiscussion Topics

DNS Overview and History Terms and Concepts

Hosts and Host Names Namespace Domains Zones


DNS OverviewDNS Overview

Name Resolution Service Resolves host names (www.Microsoft.com) to IP Addresses

(192.168.0.1) Clients issue DNS Queries to obtain IP address of target host

Provides hierarchical computer naming system Domain Name Space

Distributed database of name mapping Name Servers store records in DNS Zones Each Zone contains mapping for its namespace


DNS HistoryDNS History

Originated in early days of Internet Response to dramatic increase in number of hosts in

1980s Hosts File vs. DNS Enabled network-wide use of user-friendly computer

names


More DNS HistoryMore DNS History

RFC-based Original implementation was Berkeley Internet Name

Domain (BIND) MS DNS Implementations:

NT operating system 4.0 (Basic service, RFC-based) Windows® 2000 (New Version)

► Expanded Functionality► RFC-compliant, but with new features► Grows RFC spec for DNS► Primary name resolution method for Active Directory and MS

networking environment


DNS Terms and ConceptsDNS Terms and Concepts

Defining DNS Terms leads to better understanding of Key Concepts…


What is a “Host”? What is a “Host”?

Host A Computer or device on a network running the TCP/IP

Protocol, with an assigned IP address.


What’s in a Host Name?What’s in a Host Name?

Host Name A “friendly name” associated with a TCP/IP host Used in client syntax to locate and connect to server Multi-part (or multi-”label”) name associated with a DNS

“domain name”


Namespace and DomainsNamespace and Domains

Name Resolution The translation of hostname to IP Address Required for communication on a TCP/IP network Performed by DNS

Domain Name Space Hierarchical naming tree used by DNS to identify and locate a

given host in a given domain relative to the root of the tree Domain

A recognized partition within the overall Domain Name Space.


Domain Name SpaceDomain Name Space


Namespace With DomainsNamespace With Domains


Server and FQDNServer and FQDN

DNS Server A computer running the Domain Naming System (DNS)

Service or daemon Hosts a namespace or portion of a namespace (Domain) Is “authoritative” for a namespace or Domain Resolves name resolution requests submitted by DNS Clients

(DNS Client=Resolver) Fully Qualified Domain Name (FQDN)

Combined hostname and domain name that provide a complete path to the hostname relative to the root of the DNS tree. (SRV01.Sales.South.NewCorp.Com)


DNS Naming StandardsDNS Naming Standards

Limited subset of ACSII character set A-Z a-z 0-9

Hyphen (-) Underscore (_) is reserved character


How DNS Data is Stored and MaintainedHow DNS Data is Stored and Maintained

Zone Resource Records Zone Types Delegation


SummarySummary

DNS History Hosts and Host Names Namespace Domains Zones


Continue …Continue …

Module 1 Section 2

DNS Concepts and Terminology:Zones, Records, and Delegation




Module 1Module 1

DNS Concepts and TerminologyDNS Concepts and TerminologySection 2Section 2

Zones, Records, and DelegationZones, Records, and Delegation

This section defines and explains DNS zones, resource records, and delegation of namespace authority.

Presented by Mark Simos & Bill NoonanTime required 28 minutesDemonstrations NoneLab sessions None



Zone Resource Records Zone Types Delegation Hosts File


In the Zone – DNS Zone TerminologyIn the Zone – DNS Zone Terminology

Zone A collection of name/address mappings for hosts within a

contiguous portion of the DNS namespace Zone Data is maintained on a DNS Server:

Flat “zone file” containing lists of mappings Stored in Active Directory database

A server is “authoritative” for a zone if it can resolve names and addresses requested by clients In most cases a zone corresponds to a domain, subdomain, or

contiguous series of domains and subdomains


Resource Records and Record TypesResource Records and Record Types

DNS Resource Records (RR) Individual entries in a DNS database that maps one type of

name or address to another. Record Types:

A (Host) PTR (Pointer) NS (NameServer) SOA (Start of Authority) SRV (Service Record) CNAME (Alias) MX (Mail Exchanger) Etc.


Record Types DefinedRecord Types Defined

A (Host) Primary entry for any computer or device on the network Resolves host name to IP address

PTR (Pointer) Reverse lookup entry, resolves IP Address to host name

NS (Name Server) Identifies a named host as a DNS Server for a zone

SOA (Start of Authority) Identifies primary DNS name server with “authority” to resolve

names for a given zone


Additional Record Types DefinedAdditional Record Types Defined

SRV (Service Record) Indicates availability of a given service on a given host Example:

► Windows® 2000 Domain Controllers register SRV Records which are used to direct client logon requests…

CNAME (Alias) Typically relates a well known “common name” to a specific

host name. Example:

► “WWW” is commonly registered as a CNAME record for Web servers

MX (Mail Exchanger) Identifies E-Mail Servers Example: MS Exchange registers an MX record


These resource records were dynamically added to the DEMO.COM zone when SERVER1 came

up for the first time.

SOA – This server is authoritative for DEMO.COM

NS – This is a Name Server for DEMO.COM

MX – It is a mail server

A – Name/IP Mapping for Server1

CNAME – This server will recognize WWW in a DNS query.


DNS Zone TypesDNS Zone Types

Forward Lookup Zone Resolves Names to IP Address

► A (Host) Record► SRV ► CNAME► Etc.

Reverse Lookup Zone Resolves IP Addresses to Host Names

► PTR (Pointer) Records


DNS Zone Types (cont)DNS Zone Types (cont)

AD Integrated Zone DNS zone data stored in Active Directory database May be secured via access control list (ACL) Both Forward and Reverse Zones may be stored in Active

Directory


Primary and Secondary ZonesPrimary and Secondary Zones

Standard Primary Zone DNS zone stored in a flat text file on a server’s local file

system. One writable copy of Primary Zone per DNS Zone Most commonly created and populated by Administrator Dynamic updated of Zones supported in Win2k

Standard Secondary Zone Read-only copy of Zone stored on Secondary DNS Server Receives updates from Primary via “zone transfer” process


This DNS server that is authoritative for the Root Zone “owns” the entire

namespace.

It is the “top” of the hierarchy and does not refer to or forward queries

to any other server.

(Keep in mind that DNS is an “inverted tree” hierarchy)

The Root or “dot” (.) ZoneThe Root or “dot” (.) Zone

More on how DNS queries are

processed later in the course!


DelegationDelegation

The process of assigning authority over a portion of the DNS namespace to another administrative entity

Adds records in the DNS database. “Glue” Record NS record identifies delegated zone and Name Server with

authority for that zone. Wizard-driven process in Windows® 2000


Delegation Example (Basic)Delegation Example (Basic)

Admin at Contoso.Com level of namespace

delegates authority for West.Contoso.Com and

offloads administration of DNS for that part of the

namespace

Delegation records enable the upper level server to locate a Name Server for the delegated zone when attempting to

resolve queries for clients. This also reduces the workload on Servers and

Admins at Contoso.Com level

West.Contoso.Com now has it’s own Admin and DNS Server to resolve

queries in that part of the namespace/company.


The Hosts FileThe Hosts File

Hosts File Text file maintained locally on the host to provide Name/IP

Mappings Alternative resolution source to DNS May be used instead of or in conjunction with DNS Because it is maintained by the local user it may be error-

prone► Out of date► Incorrect entries

Location Windows NT® operating system and Win2k store the hosts file

in the %SYSTEMROOT%\System32\etc\HOSTS file.


SummarySummary

Zone Resource Records Zone Types Delegation Hosts File



Module 1 Section 3

DNS Concepts and Terminology:Queries




Module 1Module 1

DNS Concepts and TerminologyDNS Concepts and TerminologySection 3Section 3

QueriesQueries

This section discusses DNS queries, recursion, and referral.

Presented by Mark Simos & Bill NoonanTime required 10 minutesDemonstrations NoneLab sessions None



Terms and Concepts DNS Query DNS Query Types Recursion Referrals Recursive and Iterative Queries


DNS QueriesDNS Queries

Query A request for name

resolution to a DNS server.

Both DNS clients and DNS servers can initiate a query for name resolution.

In a typical query, a DNS Client (Resolver) will submit a target host name to a DNS Server in order to learn the IP Address associated with the Host Name.If the DNS Server cannot provide resolution, it may in turn query another DNS Server.

More detail on how queries are resolved is provided

later in the course!


Finding the Answer to a DNS QueryFinding the Answer to a DNS Query

If server is authoritative for namespace of query: Checks Cache Checks Zone Returns requested address OR Returns authoritative “NO!”


Finding the Answer to a DNS Query (cont)Finding the Answer to a DNS Query (cont)

If local DNS Server is not authoritative for namespace of query: Forwarder

► DNS Server “forwards” unresolvable queries to specific server. Root Hints

► DNS Server uses well-known addresses of multiple root servers to “walk the DNS tree” to answer

► Preconfigured on Windows® 2000 to point to well-known Internet root servers

More detail on this process later in the class!


ForwarderForwarder

DNS Servers forward queries for unknown namespaces to designated “Forwarders”

Forwarders Handle all non-local queries Enabling forwarders allocates burden

of resolving unknown names to designated server(s)


Root HintsRoot Hints

Pre-configured list of “well-known” Internet root servers Used by local DNS or Forwarder to reach name servers

outside of local namespace For Windows® 2000, maintained as CACHE.DNS file

under: “%WinntRoot%\system32\drivers\etc”


Query Recursion and ReferralQuery Recursion and Referral

Recursion A process used by DNS

to “track down” the answer.

Server will query other servers on behalf of the client,

Server returns final answer to the client when it has:

► Resolved requested address

► Authoritative “No”ReferralIf a queried DNS Server cannot provide a resolution, it may issue a Referral to the client or server that made the request. This is the address of another DNS server that may be able to resolve the query.


Recursive QueryRecursive Query

Client SideThe DNS Client typically issues a Recursive Query to its configured name server.This means, “Don’t return until you have an answer or have failed to find an answer to the query.”

Server SideWhen the Server receives a Recursive Query, unless Recursion is disabled, it “goes to work” for the client, queries other name servers until it resolves client’s query or fails to do so, and responds to client with resolved address or “failure” message.


Iterative QueryIterative Query

Asks for “Final Answer” or “Closer Server”:

Typically used between servers during resolution of client requests: Lower-level server will

issue Iterative queries to top-level servers

Reduces workload on top-level servers

Iterative Query Response Requested address Authoritative “No” A Referral, if server recognizes domain

name being queried and knows a server address for that domain.


SummarySummary

DNS Query DNS Query Types Recursion Referrals Recursive and Iterative Queries



Module 2 Section 1

DNS Processes:Client Configuration




DisclaimerDisclaimer

© 2002 Microsoft® Corporation. All rights reserved. No part of this content may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission from Microsoft®. Because Microsoft® must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft®, and Microsoft® cannot guarantee the accuracy of any information presented after the date of publication. The names of actual companies and products mentioned herein may be the trademarks of their respective owners.

THIS TRAINING CONTENT IS FOR INFORMATIONAL AND TRAINING PURPOSES ONLY, AND IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT.

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