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

Linux+ Guide to Linux Certification, 2e2 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, 2e3 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, 2e4 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, 2e5 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, 2e6 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, 2e7 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, 2e8 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, 2e9 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, 2e10 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, 2e11 Subnet Masks (continued) Figure 14-1: A sample IP address and subnet mask

Linux+ Guide to Linux Certification, 2e12 Subnet Masks (continued) = all networks = all computers 255 in an IP address can specify many hosts –Broadcast addresses

Linux+ Guide to Linux Certification, 2e13 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, 2e14 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, 2e15 TCP/IP Classes and Subnetting (continued) Table 14-1: IP address classes

Linux+ Guide to Linux Certification, 2e16 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, 2e17 Configuring a NIC Interface (continued) /etc/sysconfig/network-scripts/ifcfg- file: Stores NIC configurations Packet internet groper (ping) command: Check TCP/IP connectivity on a network

Linux+ Guide to Linux Certification, 2e18 Configuring a NIC Interface (continued) Figure 14-2: Configuring network interfaces

Linux+ Guide to Linux Certification, 2e19 Configuring a NIC Interface (continued) Figure 14-3: Configuring TCP/IP information for a network interface

Linux+ Guide to Linux Certification, 2e20 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, 2e21 Configuring a PPP Interface (continued) Figure 14-4: Adding a network interface

Linux+ Guide to Linux Certification, 2e22 Configuring a PPP Interface (continued) Figure 14-5: Selecting modem hardware

Linux+ Guide to Linux Certification, 2e23 Configuring a PPP Interface (continued) Figure 14-6: Selecting ISDN hardware

Linux+ Guide to Linux Certification, 2e24 Configuring a PPP Interface (continued) Figure 14-7: Specifying ISP settings

Linux+ Guide to Linux Certification, 2e25 Configuring a PPP Interface (continued) Information about PPP devices stored in files named ifcfg- –/etc/sysconfig/network-scripts directory Other configurations used by PPP daemon stored in /etc/ppp and /etc/isdn

Linux+ Guide to Linux Certification, 2e26 Configuring a PPP Interface (continued) Figure 14-8: Specifying TCP/IP settings

Linux+ Guide to Linux Certification, 2e27 Configuring a PPP Interface (continued) Figure 14-9: Configuring an xDSL connection

Linux+ Guide to Linux Certification, 2e28 Configuring a PPP Interface (continued) Figure 14-10: Activating a PPP connection

Linux+ Guide to Linux Certification, 2e29 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, 2e30 Name Resolution (continued) Figure 14-11: The Domain Name Space

Linux+ Guide to Linux Certification, 2e31 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, 2e32 Connecting to Network Resources Network resources: –Shared printers –Applications –Files To use network resources, must have appropriate network utilities

Linux+ Guide to Linux Certification, 2e33 Downloading Files Using FTP Most web browsers have built-in FTP utility FTP utility: Downloads files from FTP servers

Linux+ Guide to Linux Certification, 2e34 Downloading Files Using FTP (continued) Figure 14-12: Using a Web browser FTP client

Linux+ Guide to Linux Certification, 2e35 Downloading Files Using FTP (continued) Table 14-2: Common FTP commands

Linux+ Guide to Linux Certification, 2e36 Downloading Files Using FTP (continued) Table 14-2 (continued): Common FTP commands

Linux+ Guide to Linux Certification, 2e37 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, 2e38 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, 2e39 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, 2e40 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, 2e41 Accessing Post Office Protocol (POP): Download messages from server Internet Message Access Protocol (IMAP): View e- mail messages across network Simple Mail Transfer Protocol (SMTP): Sending mail from MUA to server –Mozilla Mail is most common MUA for Linux

Linux+ Guide to Linux Certification, 2e42 Accessing (continued) Figure 14-13: Configuring a mail account in Mozilla Mail

Linux+ Guide to Linux Certification, 2e43 Accessing (continued) Figure 14-14: Using Mozilla Mail

Linux+ Guide to Linux Certification, 2e44 Accessing (continued) Linux systems typically use an internal mail system designed for administration –Daemons root user when important events or problems occur mail utility: Basic reader available on most Linux distributions mutt utility: Popular MUA –Can run in a terminal

Linux+ Guide to Linux Certification, 2e45 Accessing (continued) Figure 14-15: The mutt mail user agent

Linux+ Guide to Linux Certification, 2e46 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, 2e47 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

Linux+ Guide to Linux Certification, 2e48 Summary (continued) Host names must be resolved to an IP address before network communication can take place Files, applications, and can be accessed across the network with the appropriate network utility