==OverviewPurpose / Objectives of Lab 6==[[Image:network.png|thumb|right|150px|Setting up networks is an essential operation for a system administrator. Maintaining network connectivity and securing the network are also essential operations for a system administrator.]]

== In this lab, you will learn the basics of networking by using your '''Virtual Machines''' and your '''c7host''' machine. You will first set up a virtual private network among those machines. In addition, you will learn to set up '''network names''' (to associate with server's IP Addresses), '''associate network services with port numbers''' for troubleshooting purposes, and setup '''firewall policies''' via the '''iptables''' command. <u>Main Objectives ==</u> # Configure a private (virtual ) network for Virtual Machinesyour '''VMs''' and your '''c7host''' machine# Use the CentOS GUI program to configure Configure network interfaces with static IP configuration for your Virtual Machines using both '''graphical''' and host name resolution'''command-line''' utilities.# Use the '''findlocal hostname resolution''' command to locate the configuration files modified by the GUI network configuration program# To configure a CentOS VM resolve simple server names with static network configuration without a GUI tooltheir corresponding IP Addresses# To backup Backup more recent files via (eg. '''incremental backup''') using the '''find''' command and a '''date/time-stamp ''' file.# To Use common networking utilities to associate network services with port numbers for troubleshooting purposes# Gain initial exposure to the '''iptables''' command used to configure the linux and maintain a firewall for protection and troubleshooting# Configure '''iptables''' to '''allow/disallow/forward ''' different types of network traffic using simple rules

=INVESTIGATION 1: CONFIGURING A VIRTUAL PRIVATE NETWORK= For the remainder of this course, we will focus on networking involving our VMs and our c7host machine. This lab will focus on setting up a virtual private network ('''VPN'''), connecting our VMs and c7host machine to the VPN, and configuring our VPN to make more convenient to use, troubleshoot and protect. '''Lab 7''' will focus more on configuring SSH and making access to the VPN more secure. Finally, '''lab 8''' will focus on configuring the network for fixed workstations, mobile devices, or both at the same time. There are several reasons for creating '''VPNs'''. The main reason is to '''safely connect servers together''' (i.e. to safely limit but allow share information among computer network users). This allows for a secure connection of computers yet controlling access to and monitoring (protecting) access to permitted users (discussed in more depth in lab7). 

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># Perform this section in your Make certain that <u>'''c7hostALL''' machine.# Turn off your </u> virtual machines# Start Virtual Machine Managerare powered off.

# In the '''Hostsc7host Connection Details''' Details dialog box, select the '''Virtual Networks''' tab# Disable the default configuration from starting at boot by '''<u>deselecting</u>''' '''"Autostart"''' (on boot) checkbox''' check-box and click the '''Apply''' button.# Then Stop the default network configuration by clicking on the '''stop''' button at the bottom left-side of the dialog box.

# Give your new network a name (i.e. '''network1''')then click the '''Forward''' button.# Enter In the next screen, enter in the new network IP address space:

# Disable DHCP DHCP4 by '''deselecting''' the check boxand click the '''Forward''' button twice (accepting the defaults).# Enable Network Forwarding by Selecting '''Forwarding to physical network'''# The , the destination should be '''Any physical device''' and the mode should be '''NAT'''# Proceed with changes, and select click '''Finish'''.{{Admon/note | Repeat these steps for each VM | Complete the following steps on <u>'''each'''</u> of your virtual machines.}}

<li value="1513">Now we need to We will now reconfigure each of our 3 VMs to use our new virtual network '''network1'''

<li value="1">Select the Let's start with our '''centos1 VM'''. Double-click on your '''centos1''' VM , but instead of running the VM, click on the '''view''' menu, and edit the select: '''Virtual Machine Details'''<br />(Note: the Virtual Machine window will appear - do not start virtual machine)</li> <li>Under View select '''Details'''</li>

<li>Change it to '''Virtual Network network1: NAT''' (i.e. the VPN that you just created) and click the '''Apply' : NAT'' button.</li>

# Start '''centos2''' VM and login# On your '''centos hostc7host''' machine, run <codeb>ifconfig</codeb> and make note of the IP address assigned to the <code>'''virbr1</code> ''' (i.e. "Virtual Bridge) interface. This will be the default gateway and DNS server for your VMs.# Start your '''centos1''' VM and login.# Within your centos1 VM, click '''Applications''' menu, then select '''System Tools''', and then '''Settings'''. # In the ''Settings'' Dialog Box, click on the '''Network''' icon.# For the '''Wired''' connection, click the '''settings''' button (The <u>icon</u> appears as a <u>gear</u> located at the bottom right-hand corner of the dialog box).# Select the '''IPv4''' tab. Change Address from ''Automatic (DHCP)'' to '''Manual'''.# Edit the existing wired connection, using the information displayed below:

# In the '''Addresses section''', click '''"Add"'''.# Manually set enter the IP configuration tofollowing information:#: IP Address : '''192.168.235.1211'''#: Subnet Mask : '''255.255.255.0'''#: Default Gateway : The IP address of <code>'''virbr1</code> ''' on your centos host.# Click on the '''DNS''' field and add The IP address of <code>(''virbr1</code> ''' on your centos host. ) as the primary DNS server.# Your network connection may take a couple of minutes to reconfigure connect (view When finished, check your settings, and then click the Network Manager applet in the gnome panel at the top of the screen)'''Apply''' button.# You should be able Open a terminal and issue the '''ifconfig''' command to use confirm the service commands to restart your network:#:<b><code><span style="color:#3366CC;font-size:1.2em;">service network stop</span></code></b>#:<b><code><span style="color:#3366CC;font-size:1IP ADDRESS settings change.2em;">service network start</span></code></b># Verify your new interface by examining the output of <b><code><span style="color:#3366CC;font-size:1.2em;">ifconfig</span></code></b># To verify that centos2 has '''centos1'''VM is now connected to the correct default gateway configured, use VPN by issuing the commands:#:<b><code><span style="colorfollowing command from your '''c7host''' machine:#3366CC;font-size:1.2em;">route -n</span></code></b><br><b><code><span style="color:#3366CC;font-size:1.2em;">ifconfig</span></code></b><br><b><code><span style="color:#3366CC;font-size:1ping 192.168.2em;">nslookup</span></code></b><br><b><code><span style="color:#3366CC;font-size:1235.2em;">ping11</span></code></b>

# Keep your '''centos1''' VM running (you will need it running later in this lab).# Start the '''centos1centos2''' VM and login# Before we configure centos1 centos2 network configuration, we should create a timestamp file that can be used to see which files have changed as a result of using the GUI tool. Issue the following command:

# Run the network configuration tool and enter the following static configuration in the same way that you configured '''centos2centos1'''.#* IP Address: '''192.168.235.1112'''

# Verify the configuration by pinging centos host ('''192.168.235.1''') the VMs and centos2 ('''192.168.235c7host using their IP addresses.12''')#We will now create an '''Incremental Backup'''.#Run the following Linux commandas root:

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. # Start Leave your '''centos1''' and '''centos2''' VM running, but start your '''centos3''' VM , login, and login as su to '''root'''.# Use the command <code>'''ifconfig</code> ''' to list active interfaces, you should see one with a name of <code>'''eth0</code> ''' or a similar name.

# To configure your a DNS server for this VM, edit the file <code>'''/etc/resolv.conf</code>'''. Change the <code>nameserver</code> line to beread:#: <b><code><span style="color:#3366CC;font-size:1.2em;">nameserver 192.168.235.1</span></code></b># Save your editing session.# Confirm your settings work by doing the following(you might need to do the steps '''3''' and '''4''' a few times before it works; keep checking with the commands below and wait a bit before each attempt):

#: <b><code><span style="color:#3366CC;font-size:1.2em;">ping</span></code></b> (your other VM's and centos hostc7host)#: <b><code><span style="color:#3366CC;font-size:1.2em;">ssh</span></code></b> ( to your matrix Seneca's Matrix account to test your DNS)

# While we can configure network settings from the command line those settings are not persistent. To configure persistent network configurations we need to edit the configuration files. #:* Change to the '''/etc/sysconfig/network-scripts''' directory on <code></code><br>[[Image:new-network-config.png|thumb|300px|right|This diagram should show the newer network configuration of your '''c7host''' machine in relation to your '''Virtual Machines'''.]]# List the contents of the this directory and you . You should see 2 different types of files, network config scripts and network configuration files.

#::HWADDR="52:54:00:3f:5c:fa" <-- '''use the DO NOT COPY THIS VALUE! Use MAC address for YOUR interfaceusing:''' <code><span style="color:#3366CC;font-size:1.2em;">ifconfig eth0</span></code>

=INVESTIGATION 2: CUSTOMIZING THE VIRTUAL NETWORKING ENVIRONMENT TWEAKS AND OTHER USEFUL UTILITIES= Connecting a private network is an important task, but a system administrator also needs to "tweak" the network to make it '''convenient to use''', make it '''safer from unauthorized access''', and use troubleshooting utilities to help '''troubleshoot''' network connectivity problems as they occur. This investigation will expose you to some useful tricks and utilities to help accomplish this task. '''NOTE:''' Lab 7 requires that you understand these concepts and have a good general understanding how to use these troubleshooting utilities (like '''netstat''' and '''iptables'''). 

=== Testing policies iptables Policies ===

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|{{Admon/note| Interpreting iptables commands |Here is the command you just usedissue in step #15:

'''Let's break down the command to see how it works.:'''

# <ol><li value="6"> In the OUTPUT chain, add the following rule:#: <br><b><code><span style="color:#3366CC;font-size:1.2em;">iptables -A OUTPUT -j LOG</span></code></b></li># <li>The above rule tells '''iptables''' to log packets and relevant information to '''/var/log/messages'''. </li># <li>This entry in the OUTPUT policy will therefore log all packets being sent out of the machine.</li># <li>Try to access the Internet again. Because the policies have been set to DROP, you should be unsuccessful. However, every packet of data that your PC attempted to send out was logged. Let's have a look at the log file and analyze the data.#: <br><b><code><span style="color:#3366CC;font-size:1.2em;">tail /var/log/messages</span></code></b></li># <li>This command shows us the last 10 lines of the file. While there are many things being logged to this file, the last thing we did was try to access the Internet so we should be able to see the data we need. Look for a line that looks similar to the following:<br /><blockquote><code>Mar 3 09Jun 24 12:2141:03 koala-laptop 26 c7host kernel: [90775.407304] IN= OUT=wlan0 lo SRC=192127.1680.0.1.107 DST=66127.2490.900.104 1 LEN=1470 52 TOS=0x00 PREC=0x00 TTL=64 ID=19752 16442 DF PROTO=TCP SPT=45431 57151 DPT=80 5902 WINDOW=108 1024 RES=0x00 ACK PSH URGP=0</code></blockquote></li># <li>Your IP, host names and date will be different, but the one thing that should be the same is the DPT=80 value. </li># <li>When your computer tried to send OUT a request to connect to the Internet using the WWW, the computer used a destination port of 80. This is the standard port for the WWW. Because we have set the default policy to DROP it drops these packets. The problem is we are dropping all packets. What if we just want to drop the WWW packets?</li># <li>Using the commands we already know, change the default policies on all of your chains to ACCEPT. </li># <li>Open a browser and confirm that you can access the world wide web.</li># <li>Enter the command:#* <br><b><code><span style="color:#3366CC;font-size:1.2em;">iptables -I OUTPUT -p tcp -s0/0 -d 0/0 --dport 80 -j DROP</span></code></b></li># <li>Try to access the Web. If you have done everything right, you should not have been successful.</li># <li>After you have completed the test execute the following command:#* <br><b><code><span style="color:#3366CC;font-size:1.2em;">iptables -F</span></code></b><br></li><li>Using the information you have learned, try on your own to achieve the same goal as above (block www access to your computer) by using the INPUT chain instead of the OUTPUT chain.</li>{{Admon<li>After you have completed this task, flush the iptables again.</note|0/0 Addresses|Source li><li>Make sure that your ssh server is running on the host machine and destination addresses try to access it from a virtual machine of 0your choice.</0 will match li><li>Once you have confirmed that ssh is running on the host machine, insert an iptables rule on the host machine to prevent access to the ssh server from all addressesVM's on the virtual network. Therefore, they </li><li>Confirm that your rule works by testing from your VM's</li><li>Does iptables close the port? Check using ''don't do anythingnetstat''' and can be removed:</li><li>Now insert a rule on the CentOS host that would ACCEPT connections from the centos2 VM only.</li> iptables -I OUTPUT -p tcp -s0<li>Fully test your configuration.</0 -d 0li></0 --dport 80 -j DROPol>

It should be noted that all of the commands that we do here with iptables will not be persistent unless you have your configuration. That means if you re-I OUTPUT -p tcp --dport 80 boot, the default iptables configuration will be loaded. When your iptables service starts or at boot time it has to load the rules from the file '''/etc/sysconfig/iptables-j DROP}}config'''.

# Using Make a backup of the information you have learned, try on your own to achieve the same goal as above (block www access to your computer) file '''/etc/sysconfig/iptables''' by using issuing the INPUT chain instead of the OUTPUT chaincommand:<br><b><code><span style="color:#3366CC;font-size:1.2em;">iptables-save > /etc/sysconfig/iptables.bk</span></code></b># After you have completed this task, flush To make the iptables againrules '''persistent''' (i.# Make sure that your ssh server is running on the host machine and try to access it from a virtual machine of your choicee. # Once keeps rules when system restarts), you have confirmed that ssh is running on issue the host machine, insert an command: <br><b><code><span style="color:#3366CC;font-size:1.2em;">iptables rule on the host machine to prevent access to the ssh server from all VM's on the virtual network.# Confirm that your rule works by testing from your VM's# Does -save > /etc/sysconfig/iptables close the port? Check using </span></code>netstat</codeb># Now insert a rule on the CentOS host Verify that would ACCEPT connections from the centos2 VM onlyfile '''/etc/sysconfig/iptables''' exists.# Fully Restart your iptables service and test your configuration.

{{Admon'''Answer the Part 3 observations /important | Non-Persistent Changes to questions in your Host System | Complete this lab on your host system (f16host). It should be noted that all of the commands that we do here with iptables will not be persistent unless you have your configuration. That means if you re-boot, the default iptables configuration will be loadedlog book.}}'''

{{Admon/important|Time for a new backup, INCLUDING YOUR VIRTUAL HARD DRIVE!|If you have successfully completed this lab, make a new backup of your virtual machines. Remember to also make a backup of the new second virtual disk drive on '<br><br>'centos3'' Virtual hard-- drives created lab5 are image files and may have data changed as a result of performing this lab. Therefore, you now have two virtual disks on need to be backed up this hard disk image as well!''centos3'', and therefore two image files, and therefore will need two backup files.}}

# <codeol><li><span style="color:green;font-size:1.5em;">ifconfig&#x2713;</codespan> from all 3 '''centos2''' VM:<blockquote><ul><li>Contents of '''/tmp/lab6's# The contents of '' directory.</li><codeli>'''ssh''' from centos2 to the CentOS host</etcli></hostsul></codeblockquote> on each machine# The contents of your <code/li>arp</codeli><li> cache<span style="color:green;font-size:1.5em;">&# x2713;</span> '''<u>All<code/u>sshVMs''':<blockquote><ul><li>'''ifconfig''' information</codeli><li> from centos2 to the CentOS host.# Contents of '''/etc/hosts''' file<code/li></tmpul></lab6blockquote></codeli><li> directory<span style="color:green;font-size:1.5em;">&# Fresh x2713;</span>'''c7host''' machine<blockquote><ul><li>'''arp''' cache information</li><li>Contents of '''/etc/hosts''' file</li><li>Proof of backup of the virtual machines.# </li><li>A list of your '''iptables''' rules<code/li>iptables</codeul></blockquote></li><li><span style="color:green;font-size:1.5em;">&#x2713;</span> rules'''Lab6''' log-book filled out.</li></ol>

= Preparing for = Practice For Quizzes , Tests, Midterm &amp; Final Exam ==