Tài liệu Module 5: Implementing Name Resolution doc

You will outline the role of the Lmhosts file, Windows Internet Name Service WINS, and the NetBIOS name cache in resolving NetBIOS names!. DNS is a distributed database that is used in I

Contents

Overview 1

Configuring Name Resolution for Client

Computers 16

Lab A: Configuring a Client Computer for

Review 39

Module 5: Implementing Name Resolution

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Instructor Notes

This module provides students with the knowledge and skills required to configure, manage and troubleshoot name resolution Students will learn the concept of name resolution and the difference between network basic input/output (NetBIOS) and Transmission Control Protocol (TCP) host names They will learn how to configure a computer to use NetBIOS and Domain Name System (DNS) name resolution services, and how to use Windows utilities to troubleshoot name resolution problems

After completing this module, students will be able to:

! Describe the key concepts of name resolution

! Describe the differences between NetBIOS and host names

! Explain the various mechanisms that are used to perform name resolution

! Configure a computer to manage name resolution services

! Troubleshoot name resolution problems

Materials and Preparation

This section provides the materials and preparation tasks that you need to teach this module

Required Materials

To teach this module, you need the following Microsoft® PowerPoint® file 2126A_05.ppt

Preparation Tasks

To prepare for this module:

! Read all of the materials for this module

! Complete the lab

Presentation:

60 Minutes

Lab:

60 Minutes

Module Strategy

Use the following strategy to present this module:

! Introduction to Name Resolution

In this topic, you will explain the need for resolution of names to Internet Protocol (IP) addresses, and briefly describe the two forms of name-to-IP-address resolution

! NetBIOS Name Resolution

In this topic, you explain how to identify when NetBIOS names are used You will outline the role of the Lmhosts file, Windows Internet Name Service (WINS), and the NetBIOS name cache in resolving NetBIOS names

! Host Name Resolution

In this topic, you will explain how to identify the situations when host names are used You will also outline the role of the Hosts file, DNS, and the DNS resolver cache in resolving host names

! Configuring Name Resolution for Client Computers

In this topic, you will explain how to configure a variety of Microsoft client operating systems to use WINS and DNS

! Troubleshooting Name Resolution

In this topic, you will describe some of the command line utilities that can

be used when troubleshooting name resolution

Overview

! Introduction to Name Resolution

! NetBIOS Name Resolution

! Host Name Resolution

! Configuring Name Resolution for Client Computers

! Troubleshooting Name Resolution

In Microsoft® Windows® 2000 and Microsoft Windows XP, the primary means for client computers to locate and communicate with other computers on an Internet Protocol (IP) network is by using the Domain Name System (DNS) DNS is a distributed database that is used in IP networks to translate, or resolve, computer names into IP addresses

However, clients using previous versions of Windows, such as computers running Microsoft Windows 98 or Microsoft Windows NT® version 4.0, also use network basic input/output (NetBIOS) names for network communication

As a result, these clients require a method of resolving NetBIOS names to IP addresses

You can install Windows Internet Name Service (WINS) to register NetBIOS computer names and resolve them to IP addresses Implementing WINS in a Windows 2000 network ensures that clients that use a previous version of Windows can locate and communicate with network resources as needed Windows 2000 and Windows XP use DNS, but they support NetBIOS to remain backward-compatible with older networks

After completing this module, you will be able to:

! Describe various types of names and the concept of name resolution

! Describe NetBIOS and Transmission Control Protocol/Internet Protocol (TCP/IP) Host Name Resolution

! Explain the various methods of resolving NetBIOS names

! Explain the various methods of resolving host names

! Configure your computer to use either type of name resolution

! Troubleshoot name resolution problems

In this module, you will learn

about name resolution, both

of NetBIOS names and TCP

host names You will learn

how to configure your

computer for both kinds of

name resolution, and how to

troubleshoot problems

Introduction to Name Resolution

! The Process of mapping a name to an IP address

! Types of names:

" NetBIOS name

" TCP/IP host name

! Name resolution methods are configurable

Name resolution is the process of mapping a textual computer name to a

numeric IP address

NetBIOS Name Resolution

NetBIOS name resolution maps a NetBIOS name to an IP address Microsoft TCP/IP can use any of the following methods to resolve NetBIOS names:

Standard methods of resolution Description

NetBIOS name cache The local cache containing the NetBIOS names

that the local computer recently resolved NetBIOS name server (NBNS) A server implemented under RFC 1001,

Protocol standard for a NetBIOS service on a TCP/UDP transport: Concepts and methods

and RFC 1002, Protocol standard for a

NetBIOS service on a TCP/UDP transport: Detailed specifications, to provide name

resolution of NetBIOS computer names The Microsoft implementation of this standard is WINS

Local broadcast A broadcast on the local network for the IP

address of the destination NetBIOS name

Topic Objective

To define name resolution

and provide an overview of

the various methods used to

resolve names

Lead-in

To reach a remote computer

on a network, its name must

first be resolved to an IP

address

Additional Microsoft methods of

Lmhosts file A local text file that maps IP addresses to the

NetBIOS computer names of Windows networking computers on remote networks Hosts file A local text file in the same format as the 4.3

Berkeley Software Distribution (BSD) UNIX\etc\hosts file This file maps host names

to IP addresses This file is typically used to resolve host names for TCP/IP utilities DNS A server that maintains a database of IP

address/computer name (host name) mappings

Host Name Resolution

Microsoft TCP/IP can use any of the following methods to resolve host names The methods that Windows 2000 can use to resolve a host name are

configurable

Standard methods of resolution Description

Local host name The configured host name for the computer

This name is compared to the destination host name

Host file A local text file in the same format as the 4.3

Berkeley Software Distribution (BSD) UNIX\etc\hosts file This file maps host names

to IP addresses This file is typically used to resolve host names for TCP/IP utilities DNS server A server that maintains a database of IP

address/computer name (host name) mappings

Additional Microsoft methods of resolution

Description

Protocol standard for a NetBIOS service on a TCP/UDP transport: Concepts and methods

and RFC 1002, Protocol standard for a

NetBIOS service on a TCP/UDP transport: Detailed specifications, to provide name

resolution of NetBIOS computer names The Microsoft implementation of this standard is WINS

Local broadcast A broadcast on the local network for the IP

address of the destination NetBIOS name

Lmhosts file A local text file that maps IP addresses to the

NetBIOS computer names of Windows networking computers on remote networks

# NetBIOS Name Resolution

! What Is a NetBIOS Name?

! NetBIOS Name Cache

! Name Resolution Using Lmhosts

! Name Resolution Using WINS

The NetBIOS name is a computer name used with some Windows operating systems to identify computers on a network To establish communications with another computer, the name must be resolved to an IP address

Specific mechanisms exist for the resolution of NetBIOS names In Windows

2000 and most of the earlier networked versions of Windows, these are the Lmhosts file and WINS

Topic Objective

To define NetBIOS names

and examine methods for

resolving them

Lead-in

NetBIOS names have their

own resolution methods

What is a NetBIOS Name?

! NetBIOS names are 16-byte addresses that uniquely identify a process for network identification

! NetBIOS names are registered dynamically and can be:

" Used only once in a network

" Registered as unique names or group names

! Use browsing to locate shared resources on the network

NetBIOS names are a more limiting alternative for naming computers to DNS names Windows 2000 can use DNS names for most functions, but a NetBIOS name resolution method must exist on any network with computers that are running earlier versions of Windows and applications that depend on NetBIOS names

NetBIOS names are 16 bytes in length, and the NetBIOS namespace has only one level This means that NetBIOS names can be used only once in a network

In contrast, the DNS namespace has multiple levels because DNS uses a fully

qualified domain name (FQDN), which combines the host name with the name

of its domain

NetBIOS Name Registration

NetBIOS names are registered dynamically when computers and services start and when users log on A NetBIOS name can be registered as a unique name, which maps to a single address, or as a group name, which maps to multiple addresses

Because multiple services that are running on the same computer can register a computer’s NetBIOS name, several NetBIOS name registrations can be generated for the same computer name The registered name is the 15-character computer name plus a sixteenth character The sixteenth character uniquely identifies each service that uses the computer name to build its NetBIOS name

NetBIOS names are

registered dynamically when

computers and services

start and when users log on

Important

Example of NetBIOS Name Registration

An example of a service that uses a NetBIOS name is the Server service in Windows 2000, which provides file and printer sharing When you start your computer, the service registers a unique NetBIOS name that is based on the computer name The registered name is the 15-character computer name plus a sixteenth character of 0x20 The sixteenth character uniquely identifies the Server service

When you attempt to connect to a shared folder by using a NetBIOS name, a name query is initiated to search for the NetBIOS name of the Server service Communication is established when the NetBIOS name is located, and then you can connect to the server on which the shared folder is stored

Browsing

Windows 2000 creates lists of registered NetBIOS names to enable users to locate computers that contain shared resources on the network The process of

building these lists is called browsing

To access these shared resources:

1 Open My Network Places, and then double-click Entire Network

2 Click Entire contents

3 Double-click Microsoft Windows Network

4 Double-click the appropriate domain or workgroup, and then double-click the name of computer on which the resource is stored

Open Network Neighborhood to access browsing information on computers running earlier versions of Windows

For more information about browsing, see Appendix XX, Computer Browser

Service, under Additional Reading on the Web page on the Student Materials

compact disc, and the appendix, Windows 2000 Browser Service, in the TCP/IP Core Networking Guide in the Microsoft Windows 2000 Server Resource Kit

Delivery Tip

Describe the browsing

process, and demonstrate

the procedure for accessing

shared resources

Note Key Point

NetBIOS Name Cache

! A local cache containing most recently resolved NetBIOS names

! Name resolution searches the cache first

When a user initiates a Windows command, such as net use, the NetBIOS

name resolution process begins The NetBIOS name cache is checked for the NetBIOS name/IP address mapping of the destination host If the NetBIOS name is not found in the cache, the Windows client attempts to determine the IP address of the destination host by using other methods

You can view the NetBIOS name cache by using the nbtstat –c command

Topic Objective

To explain the function of

the NetBIOS name cache

Name Resolution Using Lmhosts

#This file is used by Microsoft TCP/IP

The Lmhosts file is a static file that is used to resolve the NetBIOS names of remote NetBIOS–based computers The Lmhosts file has the following characteristics:

! It resolves NetBIOS names that are used in older Windows commands, such

as net use

! Entries consist of one NetBIOS name and its corresponding IP address

! Each computer has its own file The default directory location is in the form:

\systemroot\SYSTEM32\DRIVERS\ETC

A sample Lmhosts file (Lmhosts.sam) is included in this directory

The hash symbol (#) is used to indicate a comment, and also is used to identify certain predefined keywords

Slide Objective

To describe the Lmhosts

file

Lead-in

The Lmhosts file is a static,

ASCII file that is used to

map an IP address to its

corresponding NetBIOS

name of a remote host

Delivery Tip

Use the graphic to explain

the elements in the Lmhosts

file

Key Points

The NetBIOS name cache

and file are always read

sequentially Add the most

frequently accessed

computers to the top of the

list

The #PRE-tagged entries

are added near the bottom,

because they will not be

accessed again once

TCP/IP initializes

Predefined Keywords

An Lmhosts file also contains predefined keywords, which are prefixed with a

# The following table lists the possible Lmhosts keywords:

Predefined keyword Description

#PRE Defines which entries should be initially preloaded

as permanent entries in the name cache Preloaded entries reduce network broadcasts, because names are resolved from cache rather than from broadcast

or by parsing the Lmhosts file Entries with a #PRE

tag are loaded automatically at initialization or

manually by typing nbtstat –R at a command

prompt

#DOM:[domain_name] Facilitates domain activity, such as logon validation

over a router, account synchronization, and browsing

#BEGIN_ALTERNATE

#END_ALTERNATE

Defines a redundant list of alternate locations for Lmhosts files The recommended way to

#INCLUDE remote files is using a UNC path, to

ensure access to the file Of course, the UNC names must exist in the Lmhosts file with a proper IP address to NetBIOS name translation

#INCLUDE Loads and searches NetBIOS entries in a separate

file from the default Lmhosts file Typically a

#INCLUDE file is a centrally located shared

LMHOST file

The NetBIOS name cache and file are always read sequentially Add the

most frequently accessed computers to the top of the list Add the #PRE-tagged

entries near the bottom, because they will not be accessed again once TCP/IP initializes

Note

Name Resolution Using WINS

net use x: \\france\public

3 2

NetBIOS name cache

NetBIOS name cache

NetBIOS name cache

125.112.54.29 Malaysia 149.129.10.4 Sweden 182.102.93.122 Australia

125.112.54.29 Malaysia 149.129.10.4 Sweden 182.102.93.122 Australia

1

NetBIOS Name Server

NetBIOS name = France

When a user initiates certain commands, such as net use, or uses an application

which uses NetBIOS, the NetBIOS name resolution process begins The NetBIOS name cache is checked for the NetBIOS name/IP address mapping of the destination host If the NetBIOS name is not found in the cache, the client will attempt to determine the IP address of the destination host by using other methods

If the name cannot be resolved by using the NetBIOS name cache, the NetBIOS name of the destination host is sent to the NetBIOS name server that is

configured for the source host When the NetBIOS name is resolved to an IP address, it is returned to the source host

The client attempts to locate the primary WINS server three times If there is no response, the client attempts to contact the secondary WINS server If, however, the primary WINS server notifies the client that it does not have a name/IP address mapping for the destination host, the client accepts this as the response and does not attempt to contact the secondary WINS server

Slide Objective

To explain how a NetBIOS

name is resolved to an IP

address using a NetBIOS

name server, such as a

WINS server

Lead-in

The most popular method of

resolving NetBIOS names to

IP addresses is with a

NetBIOS name server

Delivery Tip

Use the graphic to describe

how NetBIOS names are

resolved by using a

NetBIOS name server, such

as WINS

# Host Name Resolution

! What Is a Host Name?

! DNS Resolver Cache

! Name Resolution Using Hosts

! Name Resolution Using DNS

DNS is the Windows 2000 standard for naming host computers DNS provides

a hierarchical namespace as opposed to the flat namespace of NetBIOS

The mechanisms that are used for resolution of DNS names are the Hosts files, DNS itself, and the DNS resolver cache

Topic Objective

To define host names and

examine methods for

resolving them

Lead-in

Host names have their own

resolution methods

What Is a Host Name?

! An alias used to reference a TCP/IP host

! Provides a simplified way to access a TCP/IP host

! Used by PING and other TCP/IP utilities

! Entries are stored in the Hosts File or DNS

! Viewed with the Hostname Utility

Host names are used in virtually all TCP/IP environments The following list provides a description of a host name:

! A host name is an alias that is assigned to a computer by an administrator to identify a TCP/IP host The host name does not have to match the NetBIOS computer name, and can be any 256-character string Multiple host names can be assigned to the same host

! A host name simplifies the way that a user references other TCP/IP hosts Host names are easier to remember than IP addresses

! A host name can be used in place of an IP address when using the Ping utility or other TCP/IP utilities

! A host name always corresponds to an IP address that is stored in a Hosts file or in a database on a DNS or NetBIOS name server Windows 2000 also uses the Lmhosts file to map host names to IP addresses

! The Hostname utility displays the host name that is assigned to your system

By default, the host name is the same as the computer name of your Windows computer

Slide Objective

To define the host name

used by Windows 2000 and

common to UNIX

environments

Lead-in

A host name is used to

identify a TCP/IP host or

default gateway

A host name simplifies the

way a host is referenced

because names are easier

to remember than IP

addresses

DNS Resolver Cache

! Cache of most recently resolved host names

! DNS resolver cache is searched first

! Ipconfig /displaydns

Windows 2000 maintains a cache of the most recently resolved names When a name resolution is required, the cache is searched If no match is found, then other resolution methods are used

You can view the DNS resolver cache by using the ipconfig /displaydns

cache is maintained of the

most recently resolved

names

Name Resolution Using Hosts

ping HostB

2 1

Router

Name Resolution

IP Address Resolved

Hosts File

HostB = 131.107.7.29

1 Host name resolution begins when a user types a command, such as the

ping command, using the host name

2 Windows 2000 checks to see if the host name is the same as the local host name If the two names are the same, the computer has successfully resolved the name (the destination host is the same as the source host), and the process then uses the IP address of the host

3 If the two names are different, the Hosts file is parsed If the host name is found in the Hosts file, it is resolved to an IP address

4 If the host name cannot be resolved and no other resolution methods, such

as DNS, a NetBIOS name server, or the Lmhosts file, are configured, the process stops and the user receives an error message

Unlike the Lmhosts file,

which is used for remote

hosts only, the Hosts file

maps host names of both

local and remote hosts to

their IP addresses

Name Resolution Using DNS

ping HostB.training.microsoft.com

2 1

Router

Name Resolution IP Address Resolved

Domain Name System Server

Domain name = HostB.training.microsoft.com

A DNS server is an online database that is used to resolve FQDNs and other host names to IP addresses All versions of Windows 2000 can be configured to use DNS servers, and all server versions of Windows 2000 provide DNS server services Resolving a domain name by using a DNS server is similar to using a Hosts file

If Windows 2000 is configured to resolve host names by using a DNS server, the process is as follows:

When a user types a command by using an FQDN or a host name, the DNS server looks up the name in its database and attempts to resolve it to an IP address The DNS server may not be able to resolve the name: if this is the case, the DNS server can use other DNS servers to assist in the resolution process

If the DNS server does not respond to the request, additional attempts are made

at intervals of 5, 10, 20, 40, 5, 10, and 20 seconds If the DNS server does not respond to any of the attempts, and no other resolution methods, such as a NetBIOS name server or Lmhosts, are configured, the process stops, and an error is reported

# Configuring Name Resolution for Client Computers

! Configuring Client Computers to Use WINS

! Configuring Client Computers to Use DNS

You can configure your computer to use WINS name resolution or DNS name resolution Your choice of WINS name resolution or DNS name resolution depends on the version of Windows that you are running

Topic Objective

To explain how to configure

name resolution in various

Windows operating

systems

Lead-in

Client computers can be

configured to use WINS or

DNS The configuration

method varies according to

the Windows operating

system in use

Configuring Client Computers to Use WINS

Add addresses of WINS servers

Add addresses of WINS servers

Select Enable

NetBIOS over TCP/IP

Select Enable NetBIOS over TCP/IP

A WINS client uses a WINS server to resolve queries and locate resources on

IP networks In Windows, you configure a computer as a WINS client by supplying the IP addresses of WINS servers to be used in name resolution The recommended method to configure a WINS client is to make it a DHCP client, and set the appropriate TCP/IP options For more information about

DHCP, see Module 4, Implementing and Managing DHCP, in Course 2126A,

Managing a Microsoft Windows 2000 Network Environment (Prerelease)

It is also possible to configure WINS clients manually

Configuring Client Computers Running Windows 98

To configure a Windows 98 client to use a WINS server for name resolution:

1 In Control Panel, double-click Network.

2 Double-click the TCP/IP protocol that is bound to your network adapter

3 In the TCP/IP Properties dialog box, click the WINS Configuration tab.

4 Select Enable WINS Resolution, and type the IP addresses of the Primary

and Secondary WINS servers

Configuring Client Computers Running Windows NT 4.0

To configure a Windows NT 4.0 client to use a WINS server for name resolution:

1 In Control Panel, double-click Network

2 On the Protocols tab, choose the TCP/IP protocol, and then choose Properties

3 On the WINS Address tab, enter the IP addresses of the primary and

secondary WINS servers

Topic Objective

To show how to configure

your client computer to use

Configuring Client Computers Running Windows 2000

To configure a Windows 2000 client to use a WINS server for name resolution:

1 Right-click My Network Places, and choose Properties

2 Open the Properties dialog box for the connection, and then open the Internet Protocol (TCP/IP) Properties dialog box

3 Click the Advanced button, and then click the WINS tab

4 In the WINS pane, use the Add button to add new addresses of WINS servers You must also select the Enable NetBIOS Over TCP/IP option Configuring Client Computers Running Windows XP

To configure a Windows XP client to use a WINS server for name resolution:

1 Right-click My Network Places, and click Properties

2 Open the Properties dialog box for the connection, and then open the Internet Protocol (TCP/IP) Properties dialog box

3 Click the Advanced button, and then click the WINS tab

4 In the WINS pane, use the Add button to add new addresses of WINS servers You must also select the Default option or the Enable NetBIOS Over TCP/IP option