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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 Completion and Instructor "Sign-off" of network traffic using simple rulesLab 5: [[OPS235 Lab 5]]
== Required materials 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"|* Your SATA hard disk in a removable drive tray with Fedora host [http://linuxmanpages.com/man8/ifconfig.8.php ifconfig]*[http://fedoramobile.org/Members/MrHappy/system-config-network system-config-network]*[http://linuxmanpages.com/man8/route.8.php route]*[http://linuxmanpages.com/man8/ping.8.php ping]*[http://linuxmanpages.com/man8/arp.8.php arp]*[http://linuxmanpages.com/man8/netstat.8.php netstat]*[http://linuxmanpages.com/man8/iptables.8.php iptables]|*[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 3 Fedora HOWTOs:* [http://en.wikipedia.org/wiki/Virtual_network Virtual Machines installedNetwork - 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* Lab6 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 | Backup your VMs before proceeding | Stop all of your VMs and backup your VM disk images. 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 | Use the Fedora Host f17host | Complete the following steps on your main fedora host '''f17host''' computer system (f13host).}}
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# In the Virtual Machine Manager dialog box, Select '''Edit'''-> '''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 On Boot" ''' 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.}}
=== Investigation 2: How do you configure a static network using <code>system-config-network</code>. ===
{{Admon/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'''.# Select Ethernet Device and choose In the network card named <code>eth1</code>'''Addresses section''', click '''"Add"'''.# Statically Manually set the IP configurationto:#: 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 tab ''' field and add '''192.168.235.1 ''' as the primary DNS server.# Select ForwardClick '''Save''' to Finish, and then select Apply exit the Network Connections dialog box.# Your network 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 Finishrestart your network.#'''Restart your network ''' on fedora2by issuing the commands:#*<code>systemctl stop NetworkManager. service</code>#*<code>systemctl start NetworkManager.service NetworkManager restart</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>ping 192.168.235.1</code># Record '''Answer the answer to Investigation 2 observations / questions in your logbooklab log book.'''
=== Investigation 3: What files does the <code>system-config-network</code> GUI tool change?. ===
{{Admon/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>
{{Admon/note | Creating an Incremental Backup |We will now be using the <code>find</code> command to::*Locate the configuration files (contained in the <code>/etc</code> directory) that were modified by the GUI network configuration program:*Copy those configuration files to a "specified" directory for backup purposes Previously, you created a file called <code>/tmp/timestamp</code> that just contains the current date and time prior to running the network configuration toool for fedora2.. Any files that were modified by the GUI network configuration program should have a timestamp later (or newer) than the "timestamp" file you created. All the Linux TCP/IP configuration files are stored under the '''/etc''' directory or its sub-directories. The <code>find</code> command (using the correct options) can be used to only list those files that have been recently created since the timestamp date contained in the <code>/tmp/timestamp</code> file.|}} <ol> <li value="8">Run the following Linux command: <ul> <li><code>find /etc -newer /tmp/timestamp > /root/netcfg.lst</code></li> </ul> </li> <li>View the <code>/root/netcfg.lst</code> file. What does it contain?</li> <li>Create a new directory called: <code>/tmp/lab6</code></li> <li>Issue the following commands: <ul> <li><code>mkdir -p /tmp/lab6</code></li> <li><code>find /etc -newer /tmp/timestamp -exec cp {} /tmp/lab6 \;</code></li> </ul> </li> <li>View the contents of the <code>/tmp/lab6</code> directory. What does it contain?</li></ol> {{Admon/tip | Tip | Just for interest, it is relatively simple to automate your backups. You just create a Bash Shell script file using the <code>find</code> command above, give the shell script executable permissions, and use the <code>crontab</code> command to schedule when this script is to be run. If you want to learn more about shell scripting, you can take or refer to the course called '''OPS435''' .}} '''Answer the Investigation 3 observations / questions in your lab log book.''' === Investigation 4: How do I configure the network without a GUI tool?. ===
{{Admon/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? ===
# 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'''. Confirm that each host can ping all three of Refer to the other table below for information to enter in the <code>/etc/hosts by name</code> file.# Answer the investigation in your logbook.
{|class="collapsible" style="background: #c0c0c0" width="50%"
::1 localhost6.localdomain6 localhost6 fedora1
192.168.235.1 f13hostf17host
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 | 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?
=== Investigation 7: How can I see what network services or ports are active on my Fedora system? ===
{{Admon/note | Network Ports | When our Fedora system provides any services on a network, those services are accessible through a port number. All network services are configured to be accessed on a particular port number. By examining which ports are active on our system we can know what services (and points of attack) are available on our system. The ability to examine this information is important for troubleshooting network services and securing our systems. One great tool for this is the <code>netstat</code> command.}}
# On your fedora host execute the command : <code>netstat -at</code>
# This command will list all active TCP ports. Note the state of your ports.
# TCP is a connection oriented protocol that uses a handshaking mechanism to establish a connection. Those ports that show a state of LISTEN are waiting for connection requests to a particular service. For example you should see the <code>ssh</code> service in a LISTEN state as it is waiting for connections.
# On your fedora host try the command <code>netstat -atn</code>. How is this output different?
# Without the <code>-n</code> option <code>netstat</code> attempts to resolve IP addresses to host names (using /etc/hosts) and port numbers to service names (using /etc/services)
# Examine the <code>/etc/services</code> file and find which ports are used for the services : <code>ssh , ftp , http</code>
# Now execute the command <code>netstat -au</code> What is the difference between <code>-at</code> and <code>-au</code>?
# When examining UDP ports why is there no state?
#* -aun
#* -autnp
=== Investigation 8: How do I view and configure the IPTABLES firewall? -- Basic Function/Configuration ===
{{Admon/note | Use the f17host | Complete the following steps on your '''f17host''' computer system.}}
{{Admon/note | | [http://en.wikipedia.org/wiki/Iptables Iptables] is the built-in firewall for LINUX. 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 and through our computer.
'''FORWARD''' – LINUX PC's are often used as routers or gateways for other PC's. This means that data may have to be passed through this LINUX box, but the data is not intended for the LINUX PC nor is it being sent by the LINUX PC. Even though the data will go into this PC and it will exit this PC, the INPUT and OUTPUT chains do not apply here. Because the PC is acting as a router it does not actually send or receive data, it FORWARDS data from one machine to another. When this process happens, the data is checked against the FORWARD chain to see if it is allowed through. If it is the router will forward the data to it's destination. If not, the packet is dropped.}}
{{Admon/important | Non-Persistent Changes to your Host System | Complete this lab on your host system (f13hostf16host).
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 loaded.}}
# After you have completed the test execute the following command:
#* <code>iptables -F</code>
{{Admon/note| Interpreting iptables commands |This Here is the command you just used: iptables -I OUTPUT -p tcp -s0/0 -d 0/0 --dport 80 -j DROP Which can be read like this: Insert a rule into the iptables OUTPUT chain that will match any tcp packet, with any a source address, any destination address, and a deistination port of 80. Any packet that matches will be dropped.
Let's break down the command to see how it works.
The '''-p tcp''' switch tells iptables to only match TCP packets. Alternately, the protocol could be set to udp, icmp, or all.
The '''-s0/0''' switch specifies the source IP address. 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. (Since the rule will, by default, match any source address, this switch may be left out).
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. (Since the rule will, by default, match any destination address, this switch may be left out).
The switch '''--dport 80''' tells iptables to look at the destination port in the packet and see if it is equal to 80. Alternately, you can filter based on source addresses using the <code>--sport</code> switch.
'''-j''' means jump to a particular target – Basic targets are ACCEPT, DROP, REJECT, and LOG. The available targets depend on which table contains the chain.
'''DROP''' means drop the packet – make it disappear - and do not continue processing rules. '''REJECT''' is similar, but causes an error packet to be sent back to the source host. '''ACCEPT''' causes the packet to be processed. '''LOG''' causes an entry to be made in the system logs showing that the packet was processed. Note that the ACCEPT LOG target is the only one that does not stop rule-checking in the chain - so you can log a packet with one rule, and then use a later rule in the chain to DROP, REJECT, or ACCEPT it.
}}
{{Admon/note|0/0 Addresses|Source and destination addresses of 0/0 will match all addresses. Therefore, they '''don't do anything''' and can be removed:
iptables -I OUTPUT -p tcp -s0/0 -d 0/0 --dport 80 -j DROP is equivalent to: iptables -I OUTPUT -p tcp --dport 80 -j DROP}} ==== Additional Exercises Final Tasks ====
# 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.
{{Admon/note | iptables Service |When your iptables service starts or at boot time it has to load the rules from the file <code>/etc/sysconfig/iptables</code>.}}
== New Configuration ==
Now you should have the following network configuration:<br /><br />
[[Image:network-config2.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>'''virbr1'''</code>) that has a static default configuration of '''192.168.235.1/255.255.255.0'''* '''Fedora1 ''' VM has 1 active interface (<code>'''eth1'''</code>) that has a static configuration of '''192.168.235.11/255.255.255.0'''* '''Fedora2 ''' VM has 1 active interface (<code>'''eth1'''</code>) that has a static configuration of '''192.168.235.12/255.255.255.0'''* '''Fedora3 ''' VM has 1 active interface (<code>'''eth1'''</code>) that has a static configuration of '''192.168.235.13/255.255.255.0'''
# Contents of <code>/tmp/lab6</code> directory.
# Fresh backup of the virtual machines.
== Preparing for the Quizzes ==
# What is a port?