This document discusses network configuration in Linux systems. It describes static and dynamic configuration approaches. Static configuration requires manually setting the IP address, netmask, default gateway, and DNS servers. Dynamic configuration uses DHCP to automatically obtain this information from a server. The document also covers common network services and applications, such as HTTP, SMTP, SSH, and FTP.

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System Administration

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Key Knowledge Areas
Connecting machines and resources
Networking Configuration and Services
Networking
Terms and Utilities
network layers
tcp/udp
ethernet
ports
tcp/ip
addressing
ipv4
ipv6
subnet classes
subnet masks
cidr
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Main approaches to configuring a machine for network
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Configuring a machine for network access:
Static configuration
Dynamic configuration
Static configuration
uses set parameters for configuration, which is known by machine and network
and never changes.
- Generally used with servers.
Dynamic configuration
configures network machines on fly where a service on network provides all
configuration parameters to a machine when it joins the network.
- Generally used with workstations.
Network Configuration

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Dynamic configuration
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Dynamic configuration is the easiest to use.
The machine just needs to set up it’s interfaces with the DHCP protocol.
DHCP: Dynamic Host Configuration Protocol.
•A lease is obtained from the DHCP server, providing all network configuration
details for the client.
•The lease expires after some amount of time and is renewed by the client to
maintain network access.
Network Configuration

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Static configuration
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Static configuration
requires four configuration parameters in order to allow full network functionality:
•IP Address
•Netmask
•Default Gateway or Router
•DNS Server(s)
Network Configuration

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Static configuration
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Network Configuration
First two components of static configuration are IP address and netmask.
These provide LAN-level access
ifconfig Network Interface configuration tool
Ex: ifconfig eth0 192.168.0.100 netmask 255.255.255.0
Third configuration parameter is the default gateway.
Provides access to inter-networking, or moving from just the local LAN to other LAN’s
route Kernel routing table tool - Displays and manipulates network routing table
Ex: route add default gw 192.168.0.1
Fourth configuration info is List of IP addresses which provide the DNS service.
Allowing name to IP address mapping
To configure add name-server lines to /etc/resolv.conf
Ex: nameserver 192.168.7.15
- Also consider /etc/nsswitch.conf

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Static configuration
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Network Configuration
ifconfig and route directly manipulate the running kernel, and are not permanent
changes to the system. After a reboot, changes will be lost.
To make IP address, netmask and gateway changes permanent edit two config
files:
•/etc/sysconfig/network-services/ifcfg-eth0
•/etc/sysconfig/network

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Services
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Network Services
Services: hundreds, thousands of different network services.
each individual service might have one or a dozen apps which can provide the service.
Ex: HTTP, SMTP, SSH, FTP, MySQL
HTTP Hypertext Transfer Protocol:
Used to ship webpages and associated files across network. Servers: Apache, IIS, lighttpd
SMTP Simple Mail Transfer Protocol:
Delivers email messages. Popular Servers: qmail, sendmail, postfix, exchange
SSH Secure Shell:
Encrypted remote shell access. Server: OpenSSH
FTP File Transfer Protocol:
Used to move files around the network. Popular Servers: wu-ftpd, vsftpd
MySQL: Powerful open-source relational database management system
MySQL is the server and the only one - service is defined and implemented by the application

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Fim de sessão
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Fim de sessão
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