Most Linux distributions offer menu-driven or graphical-configuration tools for the network interface. Every distribution is different, but they all provide some tool. In this section, we used the Network Configuration tool provided with Red Hat 7.2.
On a Red Hat 7.2 system, the network interface is configured through the Network Configuration tool found on the Programs ^ System menu. The Network Configuration tool presents a window with four tabs:
Hardware Select the Hardware tab to add, remove, or configure a network adapter. To remove an adapter, highlight the adapter in the list presented on this tab, and click the button labeled Delete. To add an adapter, click the Add button and select the hardware type, which is either Ethernet, Modem, ISDN, or token ring. The Network Adapter Configuration window then appears. It has input boxes that accept an IRQ, the adapter memory address, the I/O port address, and the DMA request number. To configure an adapter, select the adapter from the list and click Edit. The same Network Adapter Configuration window used to add an adapter appears, giving you the chance to change the various hardware configuration values.
Devices Select the Devices tab to add, remove or configure a Linux network device. To remove a device, highlight the device in the list presented on this tab, and click the button labeled Delete. To add a device, either copy an existing device and edit the result, or click Add and select the device type. A device configuration window appropriate to the device type appears. For example, the Ethernet Device window has three tabs:
General Use this tab to enter the device name, for example, eth0, and to select whether or not the device should be started at boot time.
Protocols Use this tab to add, delete, or configure the network protocol associated with the device. TCP/IP is configured through this tab.
Hardware Device Use this tab to associate the device to a specific hardware adapter. For example, eth0 could be associated with the SMC Ultra Ethernet adapter.
Hosts Select the Hosts tab to make entries in the /etc/hosts table. The hosts file is covered in Chapter 4, "Linux Name Services."
DNS Select the DNS tab to define the Domain Name System configuration for a DNS client. Use the tab to set the system's hostname and domain name, and to provide the addresses of the name servers the system should use. DNS server configuration is covered in Chapter 4.
To use the Red Hat Network Configuration tool to enter the same network interface configuration that we created earlier with the ifconfig command; select Programs from the Start menu, System from the Programs menu, and Network Configuration from the System menu. In the Network Configuration window, select the Devices tab. On the Devices tab, highlight the eth0 device, and click Edit. In the Ethernet Device window, select the Protocols tab. On the Protocols tab, highlight TCP/IP, and click Edit. The result of this "point-and-click-fest" is shown in Figure 2.1.
The interface in the figure has already been configured. The fields and values are self-explanatory. Less the broadcast address, this is essentially the same configuration entered previously using the ifconfig command. Whether or not this is an easier way to enter the configuration values is a matter of personal opinion. In all Linux distributions, the designers of the configuration tools make some decisions about what is needed, where it should be defined, and how the interface should look. One of the great things about Linux is that if you disagree with the tool design, or if you want to do something differently, you can go directly to the commands that the tools really use to get the job done.
So far in this chapter, we have configured TCP/IP only on an Ethernet interface. This might lead you to believe that a Linux system requires TCP/IP and an Ethernet interface in order to communicate with other systems. That's not true. A Linux system can communicate without TCP/ IP, and it can be configured to run TCP/IP without an Ethernet interface. The next section looks at both capabilities.
Note Clearly, you want to use TCP/IP, and you want to use your Ethernet interface. The features examined in the next section do not replace TCP/IP and Ethernet. Instead, they are additional capabilities that permit you to use the computer's serial interface in ways that would not be possible on some other network server systems.
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