lesson 31. name resolution. objectives at the end of this presentation, you will be able to:
TRANSCRIPT
• 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.
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.
• 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.
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.
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 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
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.