Linux Guide to Linux Certification, Second Edition

1
Linux Guide to Linux Certification, Second
Edition

• Chapter 14
• Network Configuration

2
Objectives

• Describe the purpose and types of networks,
  protocols, and media access methods
• Understand the basic configuration of TCP/IP
• Configure a NIC interface to use TCP/IP

3
Objectives (continued)

• Configure a modem, ISDN, and DSL interface to use
  PPP and TCP/IP
• Understand the purpose of host names and how they
  are resolved to IP addresses
• Use common network utilities to interact with
  network services

4
Networks and TCP/IP

• Network Two or more computers joined via network
  media and able to exchange information
• Local Area Networks (LANs) Computers within
  close proximity
• Wide Area Networks (WANs) Computers separated by
  large distances
• Internet service provider (ISP) Company
  providing internet access

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Networks and TCP/IP (continued)

• Routers Devices capable of transferring packets
  between networks
• Protocols Set of rules for communication between
  networked computers
• Packets Packages of data formatted by a network
  protocol
• Media access method Defines how networked
  computers share access to the physical medium

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Networks and TCP/IP (continued)

• Linux network protocols
• TCP/IP (Transfer Control Protocol/Internet
  Protocol)
• UDP/IP (User Datagram Protocol/Internet Protocol)
• IPX/SPX (Internetwork Packet Exchange/Sequence
  Packet Exchange)
• Appletalk
• DLC (Data Link Control)
• DECnet (Digital Equipment Corporation network)

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Networks and TCP/IP (continued)

• Ethernet Most common network media access method
• Token Ring Popular media access method
• Media access method usually contained on NIC or
  modem hardware

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The TCP/IP ProtocolIP Addresses

• IP address Unique number that identifies a
  networked computer
• Octets Series of four 8-bit numbers
• Unicast Directed TCP/IP communication between
  two computers

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The TCP/IP ProtocolIP Addresses (continued)

• IP addresses composed of two parts
• Network ID Network computer is located on
• Host ID Single computer on that network
• Cannot have two computers with same host ID on a
  network
• Only computers with same network ID can
  communicate without a router

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Subnet Masks

• Define which part of IP address is the network ID
  and which part is the host ID
• Series of four 8-bit numbers
• ANDing Calculate network and host IDs from an IP
  address and subnet mask
• Compare binary bits

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Subnet Masks (continued)
Figure 14-1 A sample IP address and subnet mask
12
Subnet Masks (continued)

• 0.0.0.0 all networks
• 255.255.255.255 all computers
• 255 in an IP address can specify many hosts
• Broadcast addresses

13
Default Gateway

• IP address on router that sends packets to remote
  networks
• Routers can distinguish between different
  networks
• Move packets between them
• Have assigned IP addresses on each attached
  network

14
TCP/IP Classes and Subnetting

• IP address class defines default subnet mask of
  associated device
• Multicast TCP/IP communication destined for a
  certain group of computers
• Class D addresses
• Subnetting Divide a large network into smaller
  networks
• Control traffic flow
• Take bits from host ID, give to network ID

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TCP/IP Classes and Subnetting (continued)
Table 14-1 IP address classes
16
Configuring a NIC Interface

• ifconfig command Assign TCP/IP configuration to
  a NIC
• Also used to view configuration of all network
  interfaces in computer
• dhclient command Receive TCP/IP configuration
  from DHCP or Boot Protocol (BOOTP) server

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Configuring a NIC Interface (continued)

• /etc/sysconfig/network-scripts/ifcfg-ltinterfacegt
  file Stores NIC configurations
• Packet internet groper (ping) command Check
  TCP/IP connectivity on a network

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Configuring a NIC Interface (continued)
Figure 14-2 Configuring network interfaces
19
Configuring a NIC Interface (continued)
Figure 14-3 Configuring TCP/IP information for a
network interface
20
Configuring a PPP Interface

• Run TCP/IP over serial lines
• Use a WAN protocol
• Three common Point-to-Point Protocol (PPP)
  technologies
• Modems
• ISDN
• DSL

21
Configuring a PPP Interface (continued)
Figure 14-4 Adding a network interface
22
Configuring a PPP Interface (continued)
Figure 14-5 Selecting modem hardware
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Configuring a PPP Interface (continued)
Figure 14-6 Selecting ISDN hardware
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Configuring a PPP Interface (continued)
Figure 14-7 Specifying ISP settings
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Configuring a PPP Interface (continued)

• Information about PPP devices stored in files
  named ifcfg-ltInternetServiceProviderNamegt
• /etc/sysconfig/network-scripts directory
• Other configurations used by PPP daemon stored in
  /etc/ppp and /etc/isdn

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Configuring a PPP Interface (continued)
Figure 14-8 Specifying TCP/IP settings
27
Configuring a PPP Interface (continued)
Figure 14-9 Configuring an xDSL connection
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Configuring a PPP Interface (continued)
Figure 14-10 Activating a PPP connection
29
Name Resolution

• Hostnames User-friendly computer name
• FQDN Hostname following DNS convention
• DNS Hierarchical namespace for host names
• hostname command View or set a computers host
  name

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Name Resolution (continued)
Figure 14-11 The Domain Name Space
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Name Resolution (continued)

• TCP/IP cannot identify computers via hostnames
• Must map hostnames to IP addresses
• Entries in /etc/hosts file
• ISPs list FQDNs in DNS servers on Internet
• Applications request IP addresses associated with
  FQDN

32
Connecting to Network Resources

• Network resources
• Shared printers
• Applications
• Files
• To use network resources, must have appropriate
  network utilities

33
Downloading Files Using FTP

• Most web browsers have built-in FTP utility
• FTP utility Downloads files from FTP servers

34
Downloading Files Using FTP (continued)
Figure 14-12 Using a Web browser FTP client
35
Downloading Files Using FTP (continued)
Table 14-2 Common FTP commands
36
Downloading Files Using FTP (continued)
Table 14-2 (continued) Common FTP commands
37
Accessing Files with NFS

• NFS Common method for file transfer between UNIX
  and Linux computers
• Not as common as FTP
• Mount directory from a remote computer

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Accessing Windows Files

• Mount shared Windows directory to local directory
• Filesystem must be smbfs
• smbmount command Mount directories from Windows
  computers
• smbclient utility Connect to shares on a Windows
  system
• umount command Unmount Windows directories

39
Running Remote Applications

• Access to BASH shell may be obtained by
  connecting to a server across a network
• telnet utility Most common utility used to
  obtain BASH shell over a network
• No encryption
• Secure Shell (ssh) utility Uses encryption

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Running Remote Applications (continued)

• rlogin Obtain a shell from remote computer on
  network
• r utilities allow access to remote computers
  without a password
• Trusted access Computers allowed to access a
  computer without providing a password

41
Accessing E-mail

• Post Office Protocol (POP) Download e-mail
  messages from e-mail server
• Internet Message Access Protocol (IMAP) View
  e-mail messages across network
• Simple Mail Transfer Protocol (SMTP) Sending
  mail from MUA to e-mail server
• Mozilla Mail is most common MUA for Linux

42
Accessing E-mail (continued)
Figure 14-13 Configuring a mail account in
Mozilla Mail
43
Accessing E-mail (continued)
Figure 14-14 Using Mozilla Mail
44
Accessing E-mail (continued)

• Linux systems typically use an internal mail
  system designed for administration
• Daemons e-mail root user when important events or
  problems occur
• mail utility Basic e-mail reader available on
  most Linux distributions
• mutt utility Popular MUA
• Can run in a terminal

45
Accessing E-mail (continued)
Figure 14-15 The mutt mail user agent
46
Summary

• A network is a collection of computers that are
  connected together and share information
• Protocols define the format of information that
  is transmitted across a network
• The protocol used by the Internet and most
  networks is TCP/IP
• Each computer on a TCP/IP network must have a
  valid IP address and subnet mask

47
Summary (continued)

• The /etc/sysconfig/network-scripts directory
  contains the configuration for NIC and PPP
  interfaces
• The TCP/IP configuration of a network interface
  can be specified manually or obtained
  automatically from a DHCP or BOOTP server
• Host names are used to easily identify computers
  on a network host names that follow the DNS are
  FQDNs

48
Summary (continued)

• Host names must be resolved to an IP address
  before network communication can take place
• Files, applications, and e-mail can be accessed
  across the network with the appropriate network
  utility