Red Hat Enterprise Linux 5 configuring the network

Red hat Linux provides following tools to make changes to Network configuration such as add new card, assign IP address, change DNS server, etcetera:

• GUI tool (X windows required) – system-config-network
• Command line text based GUI tool (No X windows required) – system-config-network-tui
• Edit configuration files directly, stored in /etc/sysconfig/network-scripts directory

The following instructions are compatible with CentOS, Fedora Core and Red Hat Enterprise Linux 3, 4 and 5.

Editing the configuration files stored in /etc/sysconfig/network-scripts:

First change directory to /etc/sysconfig/network-scripts/:

# cd /etc/sysconfig/network-scripts/

You need to edit / create files as follows:

• /etc/sysconfig/network-scripts/ifcfg-eth0 : First Ethernet card configuration file
• /etc/sysconfig/network-scripts/ifcfg-eth1 : Second Ethernet card configuration file

To edit/create the first NIC file, type the following command:

# vi ifcfg-eth0

Append/modify as follows:

# Intel Corporation 82573E Gigabit Ethernet Controller (Copper)
DEVICE=eth0
BOOTPROTO=static
DHCPCLASS=
HWADDR=00:30:48:56:A6:2E
IPADDR=10.251.17.204
NETMASK=255.255.255.0
ONBOOT=yes

Save and close the file. Define the default gateway (router IP) and hostname in /etc/sysconfig/network file:

# vi /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=host.domain.com
GATEWAY=10.251.17.1

Save and close the file. Restart networking:

# /etc/init.d/network restart

Make sure you have correct DNS server defined in /etc/resolv.conf file. Try to ping the gateway, and other hosts on your network. Also check if you can resolv host names:

# nslookup host.domain.com

And verify if the NTP servers are correct in /etc/ntp.conf, and if you can connect to the time server, by running the ntpdate command against one of the NTP servers:

# ntpdate 10.20.30.40

This should synchronize system time with time server 10.20.30.40.