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[[Category:OPS235]]
{{Admon/caution|Draft Lab|This lab has NOT been released for regular distribution. When the lab is ready to be released, this caution banner will disappear.}}
= Configuring a Network Using Virtual Machines =
== Objectives ==
* To configure the linux firewall <code>iptables</code> to allow/disallow/forward different types of network traffic using simple rulesFedora 17 LIVE CD* Fedora 17 x86_64 Installation DVD* SATA Hard Disk (in removable disk tray)* USB Memory Stick* Lab Logbook
== Prerequisites== * Completion and Instructor "Sign-off" of Lab 5: [[OPS235 Lab 5]] ==Linux Command Online Reference ==Each Link below displays online manpages for each command (via [http://linuxmanpages.com/ http://linuxmanpages.com]): {|width="100%" cellpadding="5" width="50%"|'''Networking Utilities:'''|'''Additional Utilities:'''||- valign="top"|* [http://linuxmanpages.com/ man pagesman8/ifconfig.8.php ifconfig]*[http://fedoramobile.org/Members/MrHappy/system-config-network system-config-network]*[http://linuxmanpages.com/man8/route.8.php route] for find, ifconfig, *[http://linuxmanpages.com/man8/ping.8.php ping, ]*[http://linuxmanpages.com/man8/arp.8.php arp]*[http://linuxmanpages.com/man8/netstat, NetworkManager, nslookup, .8.php netstat]*[http://linuxmanpages.com/man8/iptables.8.php iptables, arp]|*[http://www.linuxcertif.com/man/1/systemctl/ systemctl] *[http://linuxmanpages.com/man1/find.1.php find]*[http://linuxmanpages.com/man1/tail.1.php tail]*[http://linuxmanpages.com/man1/cp.1.php cp]|} ==Resources on the web==Additional links to tutorials and HOWTOs:* [http://en.wikipedia.org/wiki/Virtual_network Virtual Network - Definition]* [http://www.reallylinux.com/docs/networkingadmin.shtml Important Linux Networking Commands] (Also refer to lab 6 notes)* [http://www.yolinux.com/TUTORIALS/LinuxTutorialNetworking.html Linux Network Configuration]* [[IPTables]] Reference* Online reading material for week 8Lab6 Notes: [http://zenit.senecac.on.ca/wiki/index.php/OPS235_Lab_6#Investigation_8:_How_do_I_view_and_configure_the_IPTABLES_firewall.3F_--_Basic_Function.2FConfiguration IPTABLES Firewall]
== Current Configuration ==
Currently you should have the following network configuration:<br /><br />[[Image:network-config1.png]]* '''Fedora host ''' has 1 active network interface (probably <code>eth0'''em1'''</code>)that receives IP configuration from the School's DHCP server.* '''Fedora host ''' has 1 active network interface (<code>'''virbr0'''</code>) that has a static default configuration of '''192.168.122.1/255.255.255.0'''* '''Fedora1 VM ''' has 1 active interface (<code>'''eth0'''</code>) that receives a dynamic configuration from your Fedora Host* '''Fedora2 VM ''' has 1 active interface (<code>'''eth0'''</code>) that receives a dynamic configuration from your Fedora Host* '''Fedora3 VM ''' has 1 active interface (<code>'''eth0'''</code>) that receives a dynamic configuration from your Fedora Host
== Lab Preparation ==
{{Admon/important | Important | It is advisable to perform a <code>yum update</code> on your Fedora host Live disc installations and all 3 VM's.}}{{Admon/important | Important system-config-network | The '''fedora1 ''' VM was installed from Live CD. It is missing the GUI Network Configuration tool we will be using. Use the command <code>yum install system-config-network</code> to install it.}}{{Admon/important | Important We will be working with Backup your 3 VM's VMs before proceeding | Backup Stop all of your VMs and backup your VM disk images and then stop all 3 VM's for . Do not start the VMs until told to start them.}}
== Lab Investigations Configuring a Network Using Virtual Machines ==
=== Investigation 1: How do you create a new virtual network. ===
{{Admon/note | Note! Use the f17host | Complete this investigation the following steps on your fedora host'''f17host''' computer system.}}
Before configuring our network we want to turn off dynamic network configuration for our Virtual Machines by turning off the "default" virtual network.
# On the fedora host your '''f17host''' machine start Virtual Machine Manager# Under In the Virtual Machine Manager dialog box, Select '''Edit'''->Host '''Connection Details '''.# In the '''Hosts''' Details dialog box, select the '''Virtual Networks ''' tab# Disable the default configuration from starting at boot by '''deselecting the ''' '''"Autostart On Boot" ''' (on boot) checkbox.# Stop the default network configuration by clicking on the '''stop ''' button at the bottom left-side of the windowdialog box.# Click on the '''add ''' button (the button resembles a "plus sign") to add a new network configuration.# Give your new network a name (i.e. '''network1''')
# Enter in the new network IP address space:
#*'''192.168.235.0/24'''# Disable DHCP by '''deselecting ''' the check box.# Enable Network Forwarding by Selecting "'''Forwarding to physical network'''# The destination should be '''Any physical device''' and the mode should be '''NAT'''# Proceed with changes, and select '''Finish'''.# Before proceeding, check the "<u>default</u>" network connection (in the Virtual Networks section) to verify '''Autostart''' is disabled, and that you have created the '''network1''' configuration. You might be required to click Apply when the default '''Autostart''' option is deselected. If you have any problems launching your VMs, then it is recommend to reboot your main system.# '''Close''' the Virtual Manager, '''reboot''' your f16host, '''log-back into your f16host computer''', and '''restart''' the Virtual Machine Manager.{{Admon/note | Repeat these steps for each VM | Complete the following steps on <u>each</u> of your virtual machines.}}<ol> <li value="15">Now we need to add our new virtual network '''network1''' to the 3 VM's<ol type="a" style="margin-left:2cm"> <li value="1">Select the '''fedora1''' VM and edit the '''Virtual Machine Details'''<br />(Note: the Virtual Machine window will appear - do not start virtual machine)</li> <li>Under View select '''Details'''</li> <li>In the '''left pane''' of the Virtual Machine window, select '''NIC:''' and note that this NIC is on the "default" virtual network</li> <li>Click on the '''Remove''' button at the bottom right-side of the dialog box.</li> <li>Click on '''Add Hardware''' on the bottom left-side of the dialog box and add a new network</li> <li>For the host device, locate and select '''Virtual Network network1''' : NAT</li> <li>Click finish to exit the Virtual Machine Details dialog box.</li></ol> </li> <li value="16">Repeat steps '''a - g''' for '''fedora2''' and '''fedora3''' VM's.</li></ol>
=== Investigation 2: How do you configure a static network using <code>system-config-network</code>. ===
{{Admon/note | Note! Use fedora2 | Complete this investigation on your fedora2 VM.}}# Start '''fedora2 ''' VM and login# On your '''fedora host ''' run <code>ifconfig</code> and make note of the IP address assigned to the <code>virbr1</code> interface. This will be your default gateway for your Vm's.[[Image:new_network_dialog.png|thumb|350px]]# Make certain to return to your fedora2 VM.# To configure a new interface on fedora2 go to System'''Applications'''->Administration'''Other'''->'''Network Connections'''.# Make certain there are no '''"Wired"''' connections (even if you have to click on the connection name and click the '''Delete''' button.# Create a new wired connection, with the "Connection Name" at the top to read '''eth1'''# Click on the '''Add''' button, and select the '''IPv4 Settings''' tab.# Change the method from "Automatic (DHCP)" to '''"NewManual" button'''.# In the '''Addresses section''', click '''"Add"'''.# Manually set the IP configuration to:#: IP Address '''192.168.235.12'''#: Subnet Mask '''255.255.255.0'''#: Default Gateway '''192.168.235.1''' (The IP address of <code>virbr1</code> on your fedora host.)# Click on the '''DNS''' field and add '''192.168.235.1''' as the primary DNS server.# Select Ethernet Device Click '''Save''' to Finish, and choose exit the Network Connections dialog box.# Your network card named connection may connect (view the Network Manager applet in the gnome panel at the top of the screen). If there is no connection after a few minutes, you should be able to right-click on the applet and click "eth1" to connect.# You should be able to use the systemctl command to restart your network.#'''Restart your network''' on fedora2 by issuing the commands:#*<code>systemctl stop NetworkManager.service</code>#*<code>systemctl start NetworkManager.service</code># Verify your new interface by examining the output of <code>ifconfig</code># To verify that fedora2 has the correct default gateway configured, enter the command: <code>route -n</code># Verify the network by using: <code>eth1ping 192.168.235.1</code>
=== Investigation 3: What files does the <code>system-config-network</code> GUI tool change?. ===
{{Admon/note | Note! Use fedora1 | Complete this investigation on your fedora1 VM.}} {{Admon/note | Backing up Files |One very important aspect of system admin is performing backups. There are many methods for backing up the data on a a computer system.<br />The following is an example of a common backup system used in Business Unix/Linux systems:<br /><br />'''Full Backup''': Backup all specified files (eg. configuration, data files, etc)<br />'''Incremental Backup''': Backup of only files that have changed since last (full) backup<br /><br />When the system is required to be fully restored, then the '''full backup''' is recovered, followed by each .<br />In this investigation, you will learn how to perform an '''incremental backup''' using the <code>find</code> utility|}} # Start '''fedora1 ''' VM and login
# Before we configure fedora1 we should create a timestamp file that can be used to see which files have changed as a result of using the GUI tool.
#* <code>date > /tmp/timestamp</code>
# Run the network configuration tool and enter the following static configuration in the same way that you configured '''fedora2'''.#* IP Address: '''192.168.235.11'''#* Subnetmask: '''255.255.255.0'''#* Default Gateway: '''192.168.235.1'''#* DNS Server: '''192.168.235.1'''# Save and quit and restart exit the network configuration tool.# Restart the NetworkManagerservice.# Verify the configuration by pinging fedora host ('''192.168.235.1''') and fedora2 ('''192.168.235.12''')
# To verify that fedora1 has the correct default gateway configured, enter the command <code>route -n</code>
=== Investigation 4: How do I configure the network without a GUI tool?. ==={{Admon/note | Note! Use fedora3 | Complete this investigation on your fedora3 VM.}}# Start '''fedora3 ''' VM and login as root# Use the command <code>ifconfig</code> to list active interfaces, you should see one with a name of <code>eth1eth0</code> or a similar name.# To configure your card with a static address use the following command:#* <code>ifconfig eth1 eth0 192.168.235.13 netmask 255.255.255.0</code>
# To configure a default gateway for that interface enter the command:
#* <code>route add default gw 192.168.235.1</code>
#* List the contents of the directory and you should see 2 different types of files, network config scripts and network configuration files.
#* look for the config file for your original interface, it should be named <code>ifcfg-eth0</code>
#* Copy that file to <code>ifcfg-eth1eth<b>N</b></code> or whatever name matches where <b>N</b> relates to your current eth interfacenumber (we will use <b>eth1</b> as an example).
#* Edit the new file for you interface and give it the following settings:
# Verify your configuration as you did before.
# Finally the kickstart file used to install this VM did not set the hostname. Edit the file <code>/etc/sysconfig/network</code> and set the hostname to <code>fedora3</code>
# Restart the <code>fedora3</code> VM.
# Login and attempt to <code>ssh</code> to your matrix account to verify the settings.
=== Investigation 5: How do I setup local hostname resolution? ===
{{Admon/note | Note! Use each machine | Complete this investigation on all of your VM's and the Fedora host.}}
{{Admon/note | Please take note! Hosts files vs. the Domain Name System | On large public networks like the Internet or even large private networks we use a network service called [http://en.wikipedia.org/wiki/Domain_Name_System Domain Name System (DNS)] to resolve the human friendly hostnames like '''fedoraproject.org''' to the computer friendly 32bit numeric addresses used by the IP protocol. On smaller ad-hoc networks we can use the <code>/etc/hosts</code> on each system to resolve names to addresses.}}
# Use the <code>hostname</code> and <code>ifconfig</code> commands on your fedora host and all 3 VM's to gather the information needed to configure the <code>/etc/hosts</code> file on the fedora host and the 3 VM's.
# Edit the <code>/etc/hosts</code> file on <u>each</u> of the '''virtual machines and the fedora host'''. Refer to the table below for information to enter in the <code>/etc/hosts</code> file.
{|class="collapsible" style="background: #c0c0c0" width="50%"
::1 localhost6.localdomain6 localhost6 fedora1
192.168.235.1 f12hostf17host
192.168.235.11 fedora1
192.168.235.12 fedora2
</pre>
|}
<ol>
<li value="3">Confirm that each host can ping all three of the other hosts by name.</li>
</ol>
'''Answer the Investigation 5 observations / questions in your lab log book.'''
== Obtaining MAC Address / Service Port / Firewall Information ==
=== Investigation 6: How do I collect the MAC (Hardware) addresses of computers on my network? ===
{{Admon/note | Note! Use your Fedora Host | Complete this investigation on your Fedora host.}}
{{Admon/note | Obtaining Remote MAC Addresses| The term '''MAC''' address stands for '''Media Access Control''' address, which provides a unique ID to prevent confusion among computer systems within a network. While we use '''32bit IP addresses addresse'''s to communicate over an internetwork, on the local ethernet network packets are delivered to a '''48bit hardware address ''' (sometimes called a MAC address). The '''ARP ''' protocol resolves 32bit IP addresses to 48bit MAC addresses by using a broadcast and caching the results. We can examine the ARP cache to get the MAC addresses of other computers on our local network.<br /><br />Being able to determine remote MAC address information is useful from troubleshooting networking programs to using '''WOL''' (Wake up on Lan) to automatically boot remote workstations via the network. In this investigation, you will learn how to obtain MAC address information for various network cards.}}
# On the fedora host <code>ping</code> each of your VM's
# Check the contents of the cache again by using the command <code>arp -n</code>
# What was the difference in output?
{{Admon/note | Use the f17host | Complete the following steps on your '''INPUT'f17host'' – If your data was allowed out and a request was sent to http://www.google.ca, this web server will send data back to your PC with an acknowledgement. Before this data can be processed by your browser, it must first be checked against the INPUT chain to see if it is allowed into the PC. If it is, your browser will process the data and move to it's next task. If it is not, the packet will be droppedcomputer system.}}
{{Admon/note | | [http://en.wikipedia.org/wiki/Iptables consists of three chains of rules – INPUT, OUTPUT and FORWARDIptables] is the built-in firewall for LINUX. Here as brief explanation While this program can be controlled by different GUI's, we are going to investigate the powerful command line interface for this program to choose what data is allowed into, out of these chainsand through our computer.
'''FORWARDOUTPUT''' – LINUX PC's are often used as routers or gateways When you want to do some research on the Web for other something, you open a browser on your PC'sand navigate to http://www.google.ca. This means that data may have When you do you are attempting to be passed through this LINUX box, but establish an HTTP or HTTPS session with the data is not intended for the LINUX PC nor is it being sent by the LINUX PCweb server at http://www.google.ca. Even though the A data will go into this PC packet is built with appropriate IP and TCP information and sent out of your computer but before it will exit this PC, the INPUT and OUTPUT chains do not apply here. Because goes out to the PC is acting as a router Internet it does not actually send or receive data, it FORWARDS data from one machine will be compared to another. When this process happens, all of the data is checked against rules in the FORWARD OUTPUT chain to see if it this data is allowed throughto go “out” of the PC. If it is the router will forward the data to it's destination. If not, allowed then the packet is dropped.
# As root on the fedora host enter the following commands at the prompt:#* <code>iptables -F</code> (This flushes out or clears all of your rules from the chains)#* <code>iptables -L</code># You should see something similar to this:<br /><br />Chain INPUT (policy ACCEPT)<br /><br />target prot opt source destination<br /><br />Chain FORWARD (policy ACCEPT)<br /><br />target prot opt source destination<br /><br />Chain OUTPUT (policy ACCEPT)<br /><br />target prot opt source destination<br /><br /># Set the default policy for the INPUT chain to DROP:#* <code>iptables -P INPUT DROP</code># Now try on your own to change the default policies for the OUPUT and FORWARD chains to DROP# Write the commands you executed in your lab book.# Can we mix these policies? Try to set the FORWARD chain policy to ACCEPT. Did it work?{{Admon/note | Chain Policies | Each chain has a default policy. In my example here the default policy is ACCEPT. This means that if data packets are checked and there is no rule that matches that packet in the chain the data will be allowed to pass to it's destination. Conversely, if the policy is set to DROP then the packet will be dropped if there is no match. Flushing the table (<code>iptables -F</code>) when an ACCEPT policy is in place will cause all packets to be accepted; flushing the table when an DENY policy is in place will cause all packets to be dropped.}}
# Execute the command <code>iptables -L</code> and check that the policies on your INPUT and OUTPUT chain are set to DROP# Open a browser and attempt to access the Internet. Were you successful?# Using the commands you have learned so far, change the policies on the INPUT and OUTPUT chains to ACCEPT# Open your browser and attempt to access the Internet again. Were you successful?# Change the policies on all of the chains to DROP# In the OUTPUT chain, add the following rule:#* <code>iptables -A OUTPUT -j LOG</code># The above rule tells <code>iptables</code> to log packets and relevant information to <code>/var/log/messages</code>. # This entry in the OUTPUT policy will therefore log all packets being sent out of the machine.# 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'''target prot opt source s have a look at the log file and analyze the data.#* <code>tail /var/log/messages</code># 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 /><br /><blockquote><code>Mar 3 09:21:03 koala-laptop kernel: [90775.407304] IN= OUT=wlan0 SRC=192.168.1.107 DST=66.249.90.104 LEN=1470 TOS=0x00 PREC=0x00 TTL=64 ID=19752 DF PROTO=TCP SPT=45431 DPT=80 WINDOW=108 RES=0x00 ACK PSH URGP=0</code></blockquote># Your IP, host names and date will be different, but the one thing that should be the same is the DPT=80 value. # 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?# Using the commands we already know, change the default policies on all of your chains to ACCEPT. # Open a browser and confirm that you can access the world wide web.# Enter the command:#* <code>iptables -I OUTPUT -p tcp -s0/0 -d 0/0 --dport 80 -j DROP</code># Try to access the Web. If you have done everything right, you should not have been successful.# After you have completed the test execute the following command:#* <code>iptables -F</code>{{Admon/note| Interpreting iptables commands |Here is the command you just used:
Let'''Chain OUTPUT (policy ACCEPT)'''s break down the command to see how it works.
The '''target prot opt source destination-I'''switch tells iptables to INSERT this line into the OUTPUT policy. This means it will be the first line in the policy. If we used a -A switch it would have appended the line and it would be the last line of the policy. If you are writing complex iptables rules where multiple matches can occur, it is important that the lines go in the right order. If you follow the -I with a number, the new rule will be inserted at that location in the chain (for example, <code>-I 3 OUTPUT</code> will insert the rule into the 3rd position in the OUTPUT chain, moving the existing rules down as necessary (the old rule #3 will become the new rule #4, for example).
The '''-p tcp''' switch tells iptables to only match TCP packets. Alternately, the protocol could be set to udp, icmp, or all.
<ol> <li value="9">'''iptables -A OUTPUT -j LOG''' The above rule tells iptables to log packets and relevant information to /var/messages. This entry in the OUPTPUT policiy will therefore log all packets being sent out Make a backup of the machine. 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. 9. Execute the following command: '''tail <code>/etc/varsysconfig/logiptables</messagescode>'''</li> This command by default shows us <li>Examine 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 needhow rules are added. Look for a line that looks similar to </li> <li>Issue the followingcommand: '''Mar 3 09:21:03 koala<code>iptables-laptop kernel: [90775.407304] IN= OUT=wlan0 SRC=192.168.1.107 DST=66.249.90.104 LEN=1470 TOS=0x00 PREC=0x00 TTL=64 ID=19752 DF PROTO=TCP SPT=45431 DPT=80 WINDOW=108 RES=0x00 ACK PSH URGP=0''' Your IP, host names and date will be different, but the one thing that should be the same is the DPT=80 value. save > /etc/sysconfig/iptables</code> When your computer tried to send OUT a request to connect to save the Internet using rules you added with the WWWiptables command, the computer used a destination port of 80above. This is the standard port for the WWW. Because we have set the default policy to it drops these packets. The problem is we are dropping all packets. What if we just want to drop the WWW packets?</li> 10. Using the commands we already know, change the default policies on all of your chains to ACCEPT. Open a browser and confirm <li>Verify that you can access the world wide web. 11. file Enter the following from the command prompt: '''<code>/etc/sysconfig/iptables -I OUTPUT -p tcp -s0</0 -d 0code> was updated with your new rules.</0 –dport 80 -j DROP'''li> This command can be read like this: Insert a line into the <li>Restart your iptables OUTPUT chain that will look at tcp information service and DROP any packet with a source address from anywhere, to a destination address to anywhere if the destination port = 80 (WWW.) Let's break down the command to see how it workstest your configuration.</li> The '''-I''' switch tells iptables <li>Write a short bash script to INSERT this line into the OUTPUT policy. This means it will be the first line in the policy. If we used add a -A switch it would have appended rule allowing the line fedora1 and it would be the last line of the policy. If you are writing complex iptables where multiple matches can occur, it is important that the lines go in the right order. Most people simply write scripts to ensure this. The fedora3 VM'''-p''' tcp switch tells iptables s to filter data by looking at TCP information in the packets. For now, we simply want connect to filter data by source and destination TCP ports so we need this switch. The '''-s0<code>ssh</0''' switch specifies code> on the source IP addressfedora host. 0</0 means a source address of “anywhere.” this has been put into the lab because your ip address will change because it is dynamically assigned. You can change this value if you want to the IP address that has been specifically assigned to your PC.li>The '''-d0</0''' switch specifies the destination address. It makes sense that this address is set to “anywhere” because if we want to block all requests to the WWW, we will never know the specific IP address of web server that is trying to be accessed.ol>