Linux+ Guide to Linux Certification, Second Edition Chapter 14 Network Configuration.
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Transcript of Linux+ Guide to Linux Certification, Second Edition Chapter 14 Network Configuration.
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 5
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
Linux+ Guide to Linux Certification, 2e 6
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)
Linux+ Guide to Linux Certification, 2e 7
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
Linux+ Guide to Linux Certification, 2e 8
The TCP/IP Protocol:IP 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
Linux+ Guide to Linux Certification, 2e 9
The TCP/IP Protocol:IP 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
Linux+ Guide to Linux Certification, 2e 10
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
Linux+ Guide to Linux Certification, 2e 11
Subnet Masks (continued)
Figure 14-1: A sample IP address and subnet mask
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 15
TCP/IP Classes and Subnetting (continued)
Table 14-1: IP address classes
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 17
Configuring a NIC Interface (continued)
• /etc/sysconfig/network-scripts/ifcfg-<interface> file: Stores NIC configurations
• Packet internet groper (ping) command: Check TCP/IP connectivity on a network
Linux+ Guide to Linux Certification, 2e 18
Configuring a NIC Interface (continued)
Figure 14-2: Configuring network interfaces
Linux+ Guide to Linux Certification, 2e 19
Configuring a NIC Interface (continued)
Figure 14-3: Configuring TCP/IP information for a network interface
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 21
Configuring a PPP Interface (continued)
Figure 14-4: Adding a network interface
Linux+ Guide to Linux Certification, 2e 22
Configuring a PPP Interface (continued)
Figure 14-5: Selecting modem hardware
Linux+ Guide to Linux Certification, 2e 23
Configuring a PPP Interface (continued)
Figure 14-6: Selecting ISDN hardware
Linux+ Guide to Linux Certification, 2e 24
Configuring a PPP Interface (continued)
Figure 14-7: Specifying ISP settings
Linux+ Guide to Linux Certification, 2e 25
Configuring a PPP Interface (continued)
• Information about PPP devices stored in files named ifcfg-<InternetServiceProviderName> – /etc/sysconfig/network-scripts directory
• Other configurations used by PPP daemon stored in /etc/ppp and /etc/isdn
Linux+ Guide to Linux Certification, 2e 26
Configuring a PPP Interface (continued)
Figure 14-8: Specifying TCP/IP settings
Linux+ Guide to Linux Certification, 2e 27
Configuring a PPP Interface (continued)
Figure 14-9: Configuring an xDSL connection
Linux+ Guide to Linux Certification, 2e 28
Configuring a PPP Interface (continued)
Figure 14-10: Activating a PPP connection
Linux+ Guide to Linux Certification, 2e 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 computer’s host name
Linux+ Guide to Linux Certification, 2e 30
Name Resolution (continued)
Figure 14-11: The Domain Name Space
Linux+ Guide to Linux Certification, 2e 31
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
Linux+ Guide to Linux Certification, 2e 32
Connecting to Network Resources
• Network resources:– Shared printers– Applications– Files
• To use network resources, must have appropriate network utilities
Linux+ Guide to Linux Certification, 2e 33
Downloading Files Using FTP
• Most web browsers have built-in FTP utility
• FTP utility: Downloads files from FTP servers
Linux+ Guide to Linux Certification, 2e 34
Downloading Files Using FTP (continued)
Figure 14-12: Using a Web browser FTP client
Linux+ Guide to Linux Certification, 2e 35
Downloading Files Using FTP (continued)
Table 14-2: Common FTP commands
Linux+ Guide to Linux Certification, 2e 36
Downloading Files Using FTP (continued)
Table 14-2 (continued): Common FTP commands
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 38
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
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 40
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
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 42
Accessing E-mail (continued)
Figure 14-13: Configuring a mail account in Mozilla Mail
Linux+ Guide to Linux Certification, 2e 43
Accessing E-mail (continued)
Figure 14-14: Using Mozilla Mail
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 45
Accessing E-mail (continued)
Figure 14-15: The mutt mail user agent
Linux+ Guide to Linux Certification, 2e 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
Linux+ Guide to Linux Certification, 2e 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