Linux+ Guide to Linux Certification, Second Edition

Presentation Transcript

Chapter 14

Network Configuration

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

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

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

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

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