Linux Guide to Linux Certification Second Edition Chapter

Linux+ Guide to Linux Certification, Second Edition Chapter 14 Network Configuration Linux+ Guide to Linux Certification, 2 e

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, 2 e 2

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, 2 e 3

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, 2 e 4

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, 2 e 5

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, 2 e 6

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, 2 e 7

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, 2 e 8

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, 2 e 9

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, 2 e 10

Subnet Masks (continued) Figure 14 -1: A sample IP address and subnet mask Linux+ Guide to Linux Certification, 2 e 11

Subnet Masks (continued) • 0. 0 = all networks • 255 = all computers • 255 in an IP address can specify many hosts – Broadcast addresses Linux+ Guide to Linux Certification, 2 e 12

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, 2 e 13

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, 2 e 14

TCP/IP Classes and Subnetting (continued) Table 14 -1: IP address classes Linux+ Guide to Linux Certification, 2 e 15

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, 2 e 16

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, 2 e 17

Configuring a NIC Interface (continued) Figure 14 -2: Configuring network interfaces Linux+ Guide to Linux Certification, 2 e 18

Configuring a NIC Interface (continued) Figure 14 -3: Configuring TCP/IP information for a network interface Linux+ Guide to Linux Certification, 2 e 19

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, 2 e 20

Configuring a PPP Interface (continued) Figure 14 -4: Adding a network interface Linux+ Guide to Linux Certification, 2 e 21

Configuring a PPP Interface (continued) Figure 14 -5: Selecting modem hardware Linux+ Guide to Linux Certification, 2 e 22

Configuring a PPP Interface (continued) Figure 14 -6: Selecting ISDN hardware Linux+ Guide to Linux Certification, 2 e 23

Configuring a PPP Interface (continued) Figure 14 -7: Specifying ISP settings Linux+ Guide to Linux Certification, 2 e 24

Configuring a PPP Interface (continued) • Information about PPP devices stored in files named ifcfg-<Internet. Service. Provider. Name> – /etc/sysconfig/network-scripts directory • Other configurations used by PPP daemon stored in /etc/ppp and /etc/isdn Linux+ Guide to Linux Certification, 2 e 25

Configuring a PPP Interface (continued) Figure 14 -8: Specifying TCP/IP settings Linux+ Guide to Linux Certification, 2 e 26

Configuring a PPP Interface (continued) Figure 14 -9: Configuring an x. DSL connection Linux+ Guide to Linux Certification, 2 e 27

Configuring a PPP Interface (continued) Figure 14 -10: Activating a PPP connection Linux+ Guide to Linux Certification, 2 e 28

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, 2 e 29

Name Resolution (continued) Figure 14 -11: The Domain Name Space Linux+ Guide to Linux Certification, 2 e 30

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, 2 e 31

Connecting to Network Resources • Network resources: – Shared printers – Applications – Files • To use network resources, must have appropriate network utilities Linux+ Guide to Linux Certification, 2 e 32

Downloading Files Using FTP • Most web browsers have built-in FTP utility • FTP utility: Downloads files from FTP servers Linux+ Guide to Linux Certification, 2 e 33

Downloading Files Using FTP (continued) Figure 14 -12: Using a Web browser FTP client Linux+ Guide to Linux Certification, 2 e 34

Downloading Files Using FTP (continued) Table 14 -2: Common FTP commands Linux+ Guide to Linux Certification, 2 e 35

Downloading Files Using FTP (continued) Table 14 -2 (continued): Common FTP commands Linux+ Guide to Linux Certification, 2 e 36

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, 2 e 37

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, 2 e 38

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, 2 e 39

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, 2 e 40

Accessing E-mail • Post Office Protocol (POP): Download e-mail messages from e-mail server • Internet Message Access Protocol (IMAP): View email messages across network • Simple Mail Transfer Protocol (SMTP): Sending mail from MUA to e-mail server – Mozilla Mail is most common MUA for Linux+ Guide to Linux Certification, 2 e 41

Accessing E-mail (continued) Figure 14 -13: Configuring a mail account in Mozilla Mail Linux+ Guide to Linux Certification, 2 e 42

Accessing E-mail (continued) Figure 14 -14: Using Mozilla Mail Linux+ Guide to Linux Certification, 2 e 43

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, 2 e 44

Accessing E-mail (continued) Figure 14 -15: The mutt mail user agent Linux+ Guide to Linux Certification, 2 e 45