Changes

[[Image:network-config-centos.png|thumb|600px|right|This diagram shows the current network configuration of your '''c7host''' machine in relation to your '''Virtual Machines'''. In this section, you will be learning to change the default network settings for both your '''c7host''' machine and '''VMs''' to belong to a '''virtual network''' using fixed IP Addresses. ]]

If we are going to setup a private network, we must do 2 major operations: First, '''define a new private network in the Virtual Manager application'''; and second, '''configure each of our VMs to connect to this new private network'''. In Part 1, we will be perform the first operation. In parts 2, 3, and 4, we will be performing the second operation for all VMS (graphical and command-line).

# Perform this section in your '''c7host''' machine.<br><br>'''NOTE:''' Before configuring our network we want to '''turn off dynamic network configuration for our Virtual Machines''' by turning off the '''"default"''' virtual network. We will then define our virtual private network. Follow the steps in order to perform these operations. <br><br>

[[Image:new_network_dialog.png|right|thumb|250px|Although the private network has been setup via the '''Virtual Machine Manager''', each virtual machine requires to change its own network setting individually (either '''graphically''' or by '''command line''').]]

# On your '''c7host''' machine, run <b>ifconfig</b> and make note of the IP address assigned to the '''virbr1''' (i.e. "Virtual Bridge) interface. This will be the default gateway and DNS server for your VMs.

# Start your '''centos1''' VM and login.

Our centos3 VM is a '''text-based only''' system, thus we cannot use a graphical tool to configure centos3 to connect to our private network. Therefore we will learn how to perform this task by using command-line tools.

# Leave your '''centos1''' and '''centos2''' VM running, but start your '''centos3''' VM, login, and su to '''root'''.

If you do not entirely understand the script that you will enter, just realize that we are using these "special storage variables" in order to make this work.

#Perform this section in your '''c7host''' machine.

After setting up a private network, it can be hard to try to remember IP addresses. In this section, we will setup your network to associate easy-to-remember server names with IP ADDRESSES.

# Complete this investigation on '''all of your VMs''' and the '''c7host''' machine.

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# Perform this section on your '''c7host''' machine.

Since Linux servers may be connected to the Internet, it is very important to run a firewall to control what comes into the computer system, what goes out of the computer system, and what may be forwarded to another computer. Linux uses the command called '''iptables''' to set the firewall rules. Although graphical programs can be used to configure iptables, it is important for students of Linux Administration to learn how to use the iptables command for more complex and automated configuration via shell scripting.

# For the remainder of this section, use your '''c7host''' machine.

The final section below teaches you to make your iptables settings permanent.

# Make a backup of the file '''/etc/sysconfig/iptables''' by issuing the command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">iptables-save > /etc/sysconfig/iptables.bk</span></code></b>