Configure Network Interfaces Using ifcfg-eth0 in CentOS46

In CentOS, network interfaces are configured through configuration files located in the `/etc/sysconfig/network-scripts/` directory. Each network interface has its own configuration file, named after the interface's name (e.g., `ifcfg-eth0` for the first Ethernet interface). These files contain various settings that determine how the interface behaves, such as its IP address, netmask, gateway, and DNS servers.

ifcfg-eth0 Configuration File

The `ifcfg-eth0` configuration file contains the following key-value pairs:
DEVICE: The name of the network interface (e.g., `eth0`)
ONBOOT: Controls whether the interface is activated on system boot (yes/no)
TYPE: The type of interface (e.g., `Ethernet`)
BOOTPROTO: The method used to obtain an IP address (e.g., `dhcp`, `static`)
IPADDR: The static IP address (if `BOOTPROTO` is set to `static`)
NETMASK: The subnet mask
GATEWAY: The default gateway
DNS1: The primary DNS server
DNS2: The secondary DNS server

Configuring a Static IP Address

To configure a static IP address, set the following options in the `ifcfg-eth0` file:
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
BOOTPROTO=static
IPADDR=192.168.1.10
NETMASK=255.255.255.0

Replace `192.168.1.10` with the desired IP address and `255.255.255.0` with the subnet mask.

Configuring a DHCP Client

To configure the interface to obtain an IP address via DHCP, set the following options in the `ifcfg-eth0` file:
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
BOOTPROTO=dhcp

Configuring a Network Gateway

If the network requires a default gateway, set the `GATEWAY` option in the `ifcfg-eth0` file:
DEVICE=eth0
GATEWAY=192.168.1.1

Configuring DNS Servers

To specify DNS servers, set the `DNS1` and `DNS2` options in the `ifcfg-eth0` file:
DEVICE=eth0
DNS1=8.8.8.8
DNS2=8.8.4.4

Applying Changes

Once the configuration changes have been made, apply them by restarting the network service:
sudo systemctl restart network

Troubleshooting

If the network interface is not working properly, refer to the following troubleshooting tips:* Check the cable connections.
* Verify that the configuration file is correct and has the proper permissions.
* Disable and re-enable the interface:
sudo ifdown eth0
sudo ifup eth0

2024-12-22

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