Howto Red Hat Enterprise Linux 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=10.6.55.114
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=10.6.55.1

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.