A Standard Linux Network Configuration

A very common setup for a Linux system is to have a single Ethernet interface and be a member of a network, as either a client, a server, or both. Here are the network settings that must be configured in order for a Linux system to communicate via TCP/IP over an Ethernet network:

  • A compatible Ethernet card must be installed and recognized by the kernel. See information about the commands lsmod, lspci, and dmesg in previous chapters for more information about hardware troubleshooting.

  • An IP address and subnet mask must be assigned to the Ethernet interface (eth0). These can be assigned manually (static values saved in a configuration file) or assigned from a DHCP server on the local subnet. On RPM-based systems such as CentOS, Red Hat, and Fedora Linux, the network configuration file is /etc/sysconfig/network-scripts/ifcfg-eth0. Values from this file are read by the startup script /etc/init.d/network, which in turn calls the command ifconfig with the appropriate values.

  • In order to communicate with other subnets, a default gateway route must be configured. This is the IP address of the device on the local network that will send your packets on to other networks. This may be a dedicated device, such as a router, or it may be a general-purpose computer (with multiple Ethernet cards) running routing software. A lower-end PC running Linux is often a good choice for a router in this instance. The default gateway route is defined in the file /etc/sysconfig/network. ...

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