Transcript Chapter 10

Chapter Overview

TCP/IP Services

TCP/IP Utilities
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Automated TCP/IP Configuration
Solutions
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Reverse Address Resolution Protocol (RARP)
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Bootstrap Protocol (BOOTP)
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Dynamic Host Configuration Protocol (DHCP)
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RARP
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Uses the same message format as Address
Resolution Protocol (ARP)
Designed for diskless workstations
Supplies an Internet Protocol (IP) address
only
No longer used
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RARP Communications
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BOOTP
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Supplies an IP address and other
Transmission Control Protocol/Internet
Protocol (TCP/IP) parameters
Can supply an executable boot file using
Trivial File Transfer Protocol (TFTP)
Requires you to manually configure
parameters for each client
Cannot allocate IP addresses automatically
Cannot prevent IP address duplication
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DHCP
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Addresses the shortcomings of RARP and
BOOTP
Dynamically allocates IP addresses from a
pool
Reclaims unused addresses
Prevents IP address duplication
Supplies all TCP/IP parameters
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DHCP Components
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Client
Server
Protocol
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DHCP Address Allocation Types
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Manual allocation
Automatic allocation
Dynamic allocation
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Manual Allocation
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The administrator assigns a permanent IP
address to the client.
Manual allocation is used for computers that
require permanent IP address assignments.
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Automatic Allocation
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The DHCP server assigns the client a
permanent IP address chosen from a pool.
Automatic allocation is used on networks
where computers are rarely moved to other
subnets.
This minimizes DHCP traffic.
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Dynamic Allocation
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The DHCP server leases to the client an IP
address chosen from a pool.
The client must periodically renew the lease
address.
Unrenewed lease addresses are returned to
the pool.
Dynamic allocation allows you to add,
remove, and relocate computers.
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The DHCP Message Format
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The DHCP Options Field Format
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DHCP Message Types
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1—DHCPDISCOVER
2—DHCPOFFER
3—DHCPREQUEST
4—DHCPDECLINE
5—DHCPACK
6—DHCPNAK
7—DHCPRELEASE
8—DHCPINFORM
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The DHCP Address Assignment
Process
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The IP Address Leasing Process
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The address assignment process is the same for all of
the allocation methods.
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Clients using manual or automatic allocation receive no
further communication after the address assignment.
Clients using dynamic allocation lease IP addresses for
a time interval specified by the server.
The client must renew the lease on a regular basis to
continue using it.
DHCP address leases are typically measured in days.
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If addresses are in short supply, a shorter lease
interval is warranted.
If computers are rarely moved to other subnets, longer
lease intervals reduce the DHCP traffic.
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DHCP
The DHCP Lease Renewal Process
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The HOSTS File
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A HOSTS file is a lookup table containing a
list of host names and their equivalent IP
addresses.
Each computer has its own HOSTS file.
As the Internet grew, the HOSTS file became
impractical, and the Domain Name System
(DNS) eventually replaced it.
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DNS Characteristics
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Defined in Request for Comments (RFC) 1034
and RFC 1035
DNS defines
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A hierarchical namespace for computer networks –
Identifies computers using names composed of 3
or more words, separated by periods.
A service for resolving names into IP addresses
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DNS Characteristics (Continue)
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Common Top Level Domains
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.edu
.gov
.mil
.com
.net
.org
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The DNS Namespace
Top Level
Domain
Second
Level
Domain
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DNS Name Resolution
The DNS Name Resolution Process
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DNS Resource Record Types
Record Type
Function
Start of Authority
(SOA)
Indicates that the name server is the authoritative source
for the domain
Name Server (NS)
Identifies the DNS servers in the domain
Address (A)
Contains a name-to-address mapping for a computer in the
domain
Canonical Name
(CNAME)
Creates an alternative (or alias) name for a computer
already represented by an Address record
Pointer (PTR)
Contains an address-to-name mapping in in-addr.arpa for a
computer in the domain
Mail Exchange
(MX)
Identifies a computer that is responsible for processing
e-mail traffic addressed to the domain
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WINS Characteristics
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Is the acronym for Windows Internet Name
Service
Is a Network Basic Input/Output System
(NetBIOS) name server
Resolves NetBIOS names into IP addresses
Used only by Microsoft Windows computers
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Ping Characteristics
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Supplied with virtually every TCP/IP
implementation
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Tests connectivity to another TCP/IP system
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Syntax: ping target
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Ping Output (Typical)
Pinging cz1 [192.168.2.10] with 32 bytes of data:
Reply
Reply
Reply
Reply
from
from
from
from
192.168.2.10:
192.168.2.10:
192.168.2.10:
192.168.2.10:
bytes=32
bytes=32
bytes=32
bytes=32
time<10ms
time<10ms
time<10ms
time<10ms
TTL=128
TTL=128
TTL=128
TTL=128
Ping statistics for 192.168.2.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum =
0ms, Average =
0ms
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Traceroute Characteristics
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Variant of the Ping program
Displays a list of the routers on the path that packets
take to a destination
Uses Echo Request and Echo Reply messages, as
Ping does
Modifies the Time To Live value in each successive
Echo Request message
Can be used to troubleshoot network
communications problems by specifying the location
of the difficulty
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IPCONFIG.EXE and WINIPCFG.EXE
Characteristics
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IPCONFIG.EXE and WINIPCFG.EXE are
Windows utilities that display TCP/IP
configuration parameters.
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Use IPCONFIG.EXE on Microsoft Windows 2000
and Microsoft Windows NT.
Use WINIPCFG.EXE on Microsoft Windows 95,
Microsoft Windows 98, and Microsoft Windows Me.
Both utilities can release and renew DHCP IP
addresses.
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ARP.EXE Characteristics
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ARP.EXE enables you to view and modify the
contents of the ARP cache.
Adding addresses to the ARP cache speeds
up the connection process.
Addresses added manually to the ARP cache
are not purged.
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Using ARP.EXE
Syntax:
ARP [-a {ipaddress}] [-n ipaddress]
[-s ipaddress hwaddress {interface}]
[-d ipaddress {interface}]
Parameter
Function
-a {ipaddress}
Displays the contents of a specific ARP cache entry
-n ipaddress
Displays the contents of the ARP cache for a
network interface
-s ipaddress hwaddress
{interface}
Adds a new entry to the ARP cache
-d ipaddress {interface}
Deletes an entry in the ARP cache
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Using NETSTAT.EXE
Syntax:
NETSTAT [interval] [-a] [-p protocol] [-n]
[-e] [-r] [-s]
Parameter
Function
interval
Refreshes the display every interval seconds
-a
Displays the current network connections and the ports that are currently
listening for incoming network connections
-p protocol
Displays the currently active connections for the protocol specified by the
protocol variable
-n
Causes the program to identify computers using IP addresses instead of names
-e
Displays incoming and outgoing traffic statistics for the network interface
-r
Displays the routing table plus the current active connections
-s
Displays detailed network traffic statistics for the IP, Internet Control Message
Protocol (ICMP), TCP, and User Datagram Protocol (UDP) protocols
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Using NBTSTAT.EXE
Syntax:
NBTSTAT [-a name] [-A ipaddress] [-c]
[-n] [-r] [-R] [-s] [-S] [-RR]
Parameter
Function
-a name
Displays the NetBIOS names registered on the computer identified
by the name variable
-A ipaddress
Displays the NetBIOS names registered on the computer identified
by the ipaddress variable
-c
Displays the contents of the local computer's NetBIOS name cache
-n
Displays the NetBIOS names registered on the local computer
-r
Displays the number of NetBIOS names registered and resolved by
the local computer, using both broadcasts and WINS
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Using NBTSTAT.EXE (Cont.)
Syntax:
NBTSTAT [-a name] [-A ipaddress] [-c]
[-n] [-r] [-R] [-s] [-S] [-RR]
Parameter
Function
-R
Purges the local computer's NetBIOS name cache of all entries and reloads
the LMHOSTS file
-s
Displays a list of the computer's currently active NetBIOS settings
(identifying remote computers by name), their current status, and the
amount of data transmitted to and received from each system
-S
Displays a list of the computer's currently active NetBIOS settings
(identifying remote computers by IP address), their current status, and the
amount of data transmitted to and received from each system
-RR
Sends name release requests to WINS, then starts refresh
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Nslookup Syntax
Syntax:
NSLOOKUP DNSname DNSserver
Parameter
Function
DNSname
Specifies the DNS name that you want to resolve
DNSserver
Specifies the DNS name or IP address of the DNS
server that you want to query for the name specified in
the DNSname variable
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Telnet
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Telnet provides remote control capabilities.
Telnet clients can execute commands on a
server and view the results.
Telnet was designed for UNIX systems.
All Windows versions include a Telnet client.
Windows 2000 and later versions have a
Telnet server.
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FTP
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You can use the File Transfer Protocol (FTP) to
transfer files between computers, create and remove
directories, rename and delete files, and manage
access permissions.
FTP was designed for UNIX computers.
FTP is the mainstay of Internet communications.
All UNIX computers have FTP client and server
capabilities.
All Windows computers have a command-line FTP
client.
Windows 2000 and Windows NT servers have an FTP
server built into Microsoft Internet Information
Services (IIS).
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Chapter Summary
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TCP/IP services
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DHCP assigns IP addresses by using automatic, manual, or
dynamic allocation.
DNS resolves host and domain names into IP addresses.
WINS resolves NetBIOS names into IP addresses.
TCP/IP utilities
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Ping tests whether one computer running TCP/IP can
communicate with another computer on the network.
Traceroute displays the path that packets take through a
network to reach their destinations.
IPCONFIG.EXE and WINIPCFG.EXE display information about
the computer’s TCP/IP configuration, and they release and
renew DHCP IP address assignments.
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Chapter Summary (Cont.)
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TCP/IP utilities (Cont.)
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ARP.EXE enables you to view and modify the contents of the
ARP cache maintained by a TCP/IP system.
Netstat displays information about a computer’s TCP/IP
connections and the traffic passing over them.
NBTSTAT.EXE displays information about NetBIOS
connections and their traffic.
Nslookup enables you to transmit DNS requests to specific
servers.
Telnet provides remote control access to another computer
on the network.
FTP lets you manage files and transfer them to and from a
remote computer.
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