Linux® Quick Fix

Some of these activities are automatically covered during a Linux installation, but you will often find yourself having to know how to modify these initial settings whenever you need to move your server to another network, add a new network interface...

You also might need to add a secondary NIC interface to your server to handle data backups. Last but not least, you might just want to play around with the server to test your skills. This section shows you how to do the most common server IP activi...

The ifup and ifdown commands can be used respectively to activate and deactivate a NIC interface. You must have an ifcfg file in the /etc/sysconfig/network-scripts directory for these commands to work. Here is an example for interface eth0: [...

The netstat -nr command will provide the contents of the routing table. Networks with a gateway of 0.0.0.0 are usually directly connected to the interface. No gateway is needed to reach your own directly connected interface, so a gateway address of 0...

Your server needs to have a single default gateway. DHCP servers automatically assign a default gateway to DHCP-configured NICs, but NICs with configured, static IP addresses will need to have a manually configured default gateway. This can be done w...

Some networks may have multiple router/firewalls providing connectivity. Here's a typical scenario: You have one router providing access to the Internet that you'd like to have as your default gateway (see the default gateway example earlier).You al...

Here's how to delete the routes added in the previous section: [root@bigboy tmp]# route del -net 10.0.0.0 netmask 255.0.0.0 \ gw 192.168.1.254 wlan0 The file /etc/sysconfig/network-scripts/route-wlan0 will also have to be updated s...

If you can't find any of the desired models in your local computer store, a model in the same family or series should be sufficient. Most cards will work, but only the fully compatible ones will provide you with error-free, consistent throughput. Li...

Configuring IP Forwarding For your Linux server to become a router, you have to enable packet forwarding. In simple terms packet forwarding enables packets to flow through the Linux box from one network to another. The Linux kernel configuration pa...

The /etc/hosts file is just a list of IP addresses and their corresponding server names. Your server will typically check this file before referencing DNS. If the name is found with a corresponding IP address, DNS won't be queried at all. Unfortunate...

As you can imagine, configuring Linux networking is just a first step in providing Internet access to your server. There always things that can go wrong that may be totally out of your control. Good systems administrators know the tools needed to be ...