Lesson 31. Name Resolution

Objectives

At the end of this Presentation, you will be able to:

• Explain the purpose of name resolution.• Identify each of the following and explain

how each relates to TCP/IP: DNS, WINS, and host files.

• Identify the normal configuration parameters for a workstation, including DNS, WINS, host name, and Internet Domain Name.

Network+ Domains covered:

• 3.11• 4.1• 4.7

A single computer may be identified in many different ways:

• A NetBEUI name like: Larry• A host name like: Workstation1• A URL like: www.heathkit.com• An IP Addresses like: 200.0.1.13• A Hardware or MAC Addresses like: 00-

00-21-0A-EF-12

The HOSTS File

• A hold over from the earliest days of the Internet.

• The original HOSTS file resided on a computer at the Stanford Research Institute’s Network Information Center.

• Its purpose: To map an IP address to a host’s name.

The HOSTS File is located in the Server at:

C:\Winnt\System32\Driver\etc\

The HOSTS file.

• This file contains the mappings of IP addresses to host names.

• Each entry should be kept as an individual line.

• The IP address is placed in the first column followed by the corresponding host name.

• The IP address and the host name should be separated by at least one space.

• Comments may be inserted and are denoted by the # (numbers) symbol.

# Indicates Comments

Maps IP AddressTo Host Name.

127.0.0.1 localhost

IP Address Host Name

127.0.0.1 localhost131.1.2.201 Workstation1 # Larry’s PC131.1.2.202 Workstation2 # Curly’s PC

IP Address Host Name Comments

# DenotesComments

HOSTS File

• Purpose – Maps IP addresses to host names.• Disadvantage – Works only with Static IP

addresses. • Used in small networks which do not use

the Domain Name System (DNS) and in older systems, especially UNIX systems.

Some Definitions

• Host name – An English-like or human-friendly name for a particular computer in a network.

• Domain Name – An English-like name for a particular network.

• Fully Qualified Domain Name (FQDN) – The complete name for a machine on a network, comprised of both the host name and the domain name.

• Universal Resource Locator (URL) – The addressing scheme used by the Internet.

The Domain Name System (DNS)

• Acts as “Directory Assistance” for Domain Names

• Maps IP Addresses to Domain Names.• A Hierarchical Network of Servers.• Distributed throughout the Internet.

Address:

http://www.ibm.com

DNS Servers

DNS Configuration Tab

Your Workstation

DNS Server

Hey, DNS Server! What is the IP

address of:www.ibm.com

?

Your Workstation

DNS Server

The correct IP address for www.ibm.com is

204.146.80.199

The Domain Name System

.COM

.EDU .GOV .INT .MIL

GE GM IBM

WWW DE IP

Top-Level Domains

Subdomains

Computer Names

“ “ “Root”

Your Workstation

LocalDNS

Server

Root DNS Server

.COM DNS Server

IBM.COM DNS Server

What is the IP address of:www.ibm.com

?

Your Workstation

LocalDNS

Server

Root DNS Server

Maybe the Root DNS Server knows.

Hey, Root DNS Server! What is the

IP Address of www.ibm.com

?

Your Workstation

LocalDNS

Server

Root DNS Server

I don’t know. Ask the .COM Server @

200.XX.XX.XX

Your Workstation

LocalDNS

Server

Root DNS ServerHey, .COM DNS Server! What is the IP

Address of www.ibm.com

?.COM DNS Server

Your Workstation

LocalDNS

Server

Root DNS Server

.COM DNS Server

I don’t know. Ask the IBM.COM Server @

199.XX.XX.XX

Your Workstation

LocalDNS

Server

Root DNS ServerHey, IBM.COM DNS Server! What is the IP

Address of www.ibm.com

?.COM DNS Server

IBM.COM DNS Server

Your Workstation

LocalDNS

Server

Root DNS Server

.COM DNS Server

IBM.COM DNS Server

The correct IP address for www.ibm.com is

204.146.80.199

Your Workstation

LocalDNS

Server

Root DNS Server

.COM DNS Server

IBM.COM DNS Server

www.ibm.com Server

Mapping host names to IP addresses

• HOSTS file• Domain Name Service

How do you map NetBIOS names to IP addresses?

• NetBIOS names used by Microsoft products.

• Two mapping systemso LMHOSTSo Windows Internet Name Service (WINS)o DNS (Windows 2000)

The LMHOSTS file

• The NetBIOS equivalent to the HOSTS file.• The LMHOSTS file does for NetBIOS

names what the HOSTS file does for host names.

• It is unique to Microsoft products.• In Windows NT 4.0 the LMHOSTS file is

located at:o C:\Winnt\System32\drivers\etc\

• Same general format as the HOSTS file.

Windows Internet Name Service (WINS)

• Unique to Microsoft Windows. • Comes with Windows NT/2000 Server. • Maps NetBIOS names to IP addresses.• Updated dynamically as new NetBIOS

names are added to the system.

• Explain the purpose of name resolution.• Identify each of the following and explain

how each relates to TCP/IP: DNS, WINS, and host files.

• Identify the normal configuration parameters for a workstation, including DNS, WINS, host name, and Internet Domain Name.