Linux+ Guide to Linux Certification, Second Edition

Linux+ Guide to Linux Certification, Second Edition

Chapter 14Network 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


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


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


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 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)



• Ethernet: Most common network media access method

• Token Ring: Popular media access method

• Media access method usually contained on NIC or modem hardware


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


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


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


Subnet Masks (continued)

Figure 14-1: A sample IP address and subnet mask


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


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


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


TCP/IP Classes and Subnetting (continued)

Table 14-1: IP address classes


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


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



Figure 14-2: Configuring network interfaces



Figure 14-3: Configuring TCP/IP information for a network interface


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


Configuring a PPP Interface (continued)

Figure 14-4: Adding a network interface



Figure 14-5: Selecting modem hardware



Figure 14-6: Selecting ISDN hardware



Figure 14-7: Specifying ISP settings



• 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



Figure 14-8: Specifying TCP/IP settings



Figure 14-9: Configuring an xDSL connection



Figure 14-10: Activating a PPP connection


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


Name Resolution (continued)

Figure 14-11: The Domain Name Space


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


Connecting to Network Resources

• Network resources:– Shared printers– Applications– Files

• To use network resources, must have appropriate network utilities


Downloading Files Using FTP

• Most web browsers have built-in FTP utility

• FTP utility: Downloads files from FTP servers


Downloading Files Using FTP (continued)

Figure 14-12: Using a Web browser FTP client



Table 14-2: Common FTP commands



Table 14-2 (continued): Common FTP commands


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


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


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


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


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


Accessing E-mail (continued)

Figure 14-13: Configuring a mail account in Mozilla Mail



Figure 14-14: Using Mozilla Mail



• 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



Figure 14-15: The mutt mail user agent

Documents

Linux+ Guide to Linux Certification, Second Edition