In this chapter, you learned some of the basic steps required to configure a LAN with Linux. There are basic hardware components that you can use on a LAN. Transmission media usually involves copper wires or fiber- optic cables. Hubs connect computers on a LAN. Switches are often used to separate a LAN into segments. Routers can transmit data between two or more LANs. Gateways can even translate between different protocol stacks, such as TCP/IP and IPX/SPX.
For several reasons, you may need to change the network configuration that you set up during the Linux installation. Perhaps the key command to configure network cards is ifconfig . You can use ifconfig to assign hardware ports and IP address information. You can even use it to activate or deactivate a network adapter. The arp command lets you check for duplicate IP addresses. The host name commands allows you to set the name of your computer as seen by various network services. Some of the key network configuration files are /etc/ hosts , /etc/resolv.conf , /etc/host.conf , and /etc/sysconfig/network .
You can work with IPv4 addresses on your LAN. Just assign one of the private IP address ranges for the computers on your LAN. With the right network mask, you can choose from private IP address ranges in Class A, Class B, and Class C. Then all you need is one public IP address to connect your LAN to the Internet. You can use CIDR to configure IP networks with nonstandard network masks.
While broadband connections are often a more cost-effective option for business, most Internet users still connect with a telephone modem. Red Hat has developed an Internet Configuration Wizard to help you connect to several types of network adapters, including telephone modems. Alternatively, the minicom utility can help you configure an Internet connection from the command-line interface.
When you troubleshoot a network, first remember that most network problems are physical. Check your cables and connections. If that doesn t solve your problems, start collecting data. Work toward identifying the cause of the problem. Research the symptoms.
If none of these approaches help, step back, take the data that you have, and use the scientific method. Linux includes a number of commands that help you collect data and identify the cause of the problem, including ifconfig , netstat , ping , and traceroute . The ifconfig command helps you make sure that your network adapter is active. The netstat command lets you check current network connections and routing tables. The ping and traceroute commands allow you to check the connectivity within the network.
Now that you know the basics of network configuration, you re ready for Chapter 22 , where you ll learn the best practices to secure your network. Red Hat Linux includes two key security systems: Pluggable Authentication Modules (PAM) and firewalls.