In lab6, you learned to connect your VMs to a VPN using a fixed IP Address. In this final lab, you will learn how to setup, and run set-up a '''DHCP server on your centos3 machine, and then test-out the DHCP server by setting up your other VMs ''' to receive an automatically assign IP addresses from the DHCP serverAddresses upon connection requests.

{|cellpadding="15" width="40%"#INVESTIGATION_3:_SECURING_THE_SSH_CONNECTION

{{Admon/important [[Image:dhcp-config.png|thumb|right| Backup your VMs before proceeding 500px| If you did not do it at The '''dhcpd.config''' file allows the Linux system administrator to customize the end of Lab 7DCHP server. Generally in this file are '''global settings''' (options that apply throughout entire network) and '''subnet declarations''' (options that apply only to that subnet). Whenever changes are made to this file, stop all of your VMs and backup your VM disk imagesthe '''DCHP service needs to be restarted''' to allow new settings to take effect.}}<br><br>'''NOTE: Any errors in this file (such as typos or missing semi-colons) can cause the DHCP server not to restart!''' ]]

{{Admon/note |ISC # Remain in your '''centos3''' VM for this section.# Click on the following link to access the online manual page for the following DHCP packages Overview | The version of DHCP server that comes with CentOS is maintained and distributed by the Internet Software Consortium (items to gain an understanding: <ul><li>[http://linux.die.net/man/8/dhcpd dhcpd]</li><li>[https://www.iscfreebsd.org)/cgi/man.cgi?query=dhcpd.conf&sektion=5&apropos=0&manpath=FreeBSD+9.0-RELEASE+and+Ports dhcpd.conf]</li><li>[http://linux.die.net/man/5/dhcp-options dhcpd-options]</li><li>[http://linux.die.net/man/5/dhcpd.leases dhcpd. The source package that you can download from ISC includes not only leases]<br><br></li></ul># Study the DHCP server, but also a DHCP client sample '''dhcpd.conf''' file to see examples of how these options are used.# Edit '''/etc/dhcp/dhcpd.conf''' and a DHCP relay agentexamine the top section of the file. CentOS separates it into two RPM packages# Look for the comment: '''"option definitions common to all supported networks"'''# Below that comment change the DHCP client package and existing global options to reflect the DHCP server packagenewer values shown below:<br><br><br>'''domain-name''' '''"ops235.org";'''<br>'''domain-name-servers''' '''192.168.235. The DHCP client package is installed by 1;'''<br><br>'''default by the workstation installation-lease-time''' '''1200;'''<br>'''max-lease-time''' '''3600;'''<br><br><br>'''Note:''' Any values for time are stated in seconds.<br><br># View your editing sessions for typos (check for missing semicolons), then save and exit your editing session.}}<br><br>

# Perform this section in your '''centos3Answer Part 2 observations / questions in your lab log book.''' VM.# To check that you have <code>dhclient</code> installed, enter the command::: <code>rpm -q dhclient</code><ol><li value="2"> If the package is not installed, you will get the message "package dhclient is not installed", otherwise, you will get the version information of the rpm package. Install the <code>dhclient</code> package if it was not installed.</li><li>Check to see if the dhcp server package is installed. If not - install it.</li><li>Enter the command to list all the files installed from the DHCP server package.</li><li>What file appears to be a sample configuration file?</li><li>Copy the sample <code>dhcpd.conf</code> file to the <code>/etc/dhcp</code> directory making sure it is named <code>/etc/dhcp/dhcpd.conf</code></li></ol>

== Part 23: What configuration options and directives need to be set in dhcpd.conf?Configuring DHCP Server for Static IP Addresses=={{Admon/note | Use your centos3 VM | Complete the following steps on your centos3 VM.}}width="40%" align="right"

# Study the man pages of <code>dhcpd<|{{Admon/code>, <code>dhcpd.conf</code>, <code>dhcp-options</code>, and <code>dhcpd.leases</code> and make notes important | Recall Secure SSH Connection Method from Lab7 | Do not forget that you made ssh more secure in your log bookthe previous lab. In particularTherefore, look up you will need to use the meaning and possible value(s), if any, for the following configuration options:::* <code>broadcast-address</code>::* <code>default-lease-time</code>::* <code>max-lease-time</code> (How is this different from <code>default-lease-time</code>?)::* <code>domain-name</code>::* <code>domain-name-servers</code>::* <code>fixed-address</code>::* <code>group</code>::* <code>hardware</code>::* <code>host</code>::* <code>host-name</code>::* <code>range</code>::* <code>routers</code>::* <code>subnet</code>::* <code>subnet-mask</code><ol><li value="2"> Study the sample <code>dhcpd.conf</code> file same command in lab7 to securely connect to see examples of how these options are usedyour VM.</li></ol>}}

# Remain in your '''centos3''' VM for this section.# Edit <code>'''/etc/dhcp/dhcpd.conf</code> ''' for a second time.# View this file for existing subnet declarations. Note the syntax and examine the top section of directive for '''range''' and the fileoption for '''routers''' (gateway).# Make the following changes to the global settingsNow, add a new subnet delcaration for your virtual network:::* <codebr>domain-name</codebr> should be set to The network address is: '''ops235192.168.235.org0/255.255.255.0'''::* <code>domain-name-servers</codebr> range of host addresses should be set from: '''51 to 60'''<br>default gateway (routers) for the virtual network is: '''192.168.235.1'''<br><br># Save your editing session, and exit the text editor.<ol><li value="6">Open another terminal window (ssh into centos3 from the centos host as user root) and issue the following command::* <br><b><code>default<span style="color:#3366CC;font-leasesize:1.2em;">tail -timef /var/log/messages</span></code> should be set to </b><br><br>(This will show you the last lines of '''20 minutes/var/log/messages'''::* continue to display new lines as they are added to the log.)<br><codebr>max-lease-time</codeli><li> should be set In your original terminal prompt attempt to start the '''1 hourdhcpd'''service.<ol/li><li value="3">Save and exit your editing sessionYou should see new lines being added to the messages file.</li>

{{Admon/note | Global Settings Affecting All Subnets | As global settings, these settings will affect <u>'''all subnets'''</u> unless they are separately declared for individual subnets.}}- valign="top"

'''Answer Part 3 observations |{{Admon/ questions tip | Troubleshooting Tip: | Troubleshooting produces the best results when you are methodical in your lab approach. Try to fix the first error mentioned before fixing subsequent errors. Often the first error may cause multiple error messages as the configuration file is parsed. When you think you have fixed the first error try to start your service and if it fails check the log bookagain. Fix one error at a time.'''}}

|}<ol><li value== Part 4: How do I configure "9">If the '''dhcpd ''' service fails to provide IP start any error messages will be logged in the messages file. Read the errors and attempt to fix your configuration file.</li><li>If the '''dhcpd''' service starts successfully you should see success messages in the log. </li><li>If your '''dhcpd''' service starts successfully, try to my virtual network?==generate errors by editing the configuration file and introduce an error by removing a semicolon or closing curly bracket.</li>{{Admon<li>Restart your '''dhcpd''' service and observe the error messages generated. This is good practice to learn how to trouble-shoot and solve dhcpd errors.</note | Use li><li>Make certain that you have corrected those errors, and that your centos3 VM | Complete dhcpd service works properly.<li>Once the dhcpd service has is running, use the '''systemctl''' command to see if the dhcpd service is enabled. If it is not enabled, use the '''chkconfig''' command to enable the following steps on your centos3 VMdhcpd service so it started automatically upon boot-up.}}</li></ol>

|- valign== Part 5: How do I test my dhcpd service on my virtual network?=="top"

|{{Admon/note | Use your centos2 and centos3 VMs Identifying DHCP Lease Transaction Information | Complete These messages record the following steps DHCP lease transaction that consists of 4 broadcast packets, DISCOVER, OFFER, REQUEST and ACKNOWLEDGE. Try researching on your centos2 and centos3 VMsthe internet how this transaction differs from a DHCP lease renewal.}}

|}# Use your '''centos2''' and '''centos3''' VMs for this section.# On a your '''centos3 ''' terminal window (via ssh from your c7host machine) make sure that the command <codebr><b>tail -f /var/log/messages</codeb> is running.# On your '''centos2 ''' VM, change the configuration of '''eth0''' (or your interface name) to receive dynamic address configuration(i.e.via graphical application, for IVP4 tab, change ''Address'' from '''Manual''' to '''DHCP''', and '''Apply''' settings)<br>([http://zenit.senecac.on.ca/wiki/index.php/OPS235_Lab_6_-_CentOS7# Save your changes and restart the Part_2:_Configuring_VM_Network_Setup_Graphically_.28system-config-network.29 Refer to Lab6, Investigation1, Part2]).<codebr>NetworkManager</codebr> serviceNote: if you are configuring via command line, make certain to restart the network for centos2.# Logout and restart your '''centos2''' VM.# Observe the messages that get loggedfrom the tail -f command as your centos2 VM starts. You should see output similar to the following:<br><br>::<pre span style="font-family:courier;">Mar 24 13:28:24 centos3 dhcpd: DHCPDISCOVER from 52:54:00:61:00:e7 via eth2</span>::<span style="font-family:courier;">Mar 24 13:28:25 centos3 dhcpd: DHCPOFFER on 192.168.235.51 to 52:54:00:61:00:e7 via eth2</span>::<span style="font-family:courier;">Mar 24 13:28:25 centos3 dhcpd: DHCPREQUEST for 192.168.235.51 (192.168.235.13) from 52:54:00:61:00:e7 via eth2</span>::<span style="font-family:courier;">Mar 24 13:28:25 centos3 dhcpd: DHCPACK on 192.168.235.51 to 52:54:00:61:00:e7 via eth2<br><br></prespan>{{Admon/note | Identifying DHCP Lease Transaction Information | These messages record the DHCP lease transaction that consists of 4 broadcast packets, DISCOVER, OFFER, REQUEST and ACKNOWLEDGE. Try researching on the internet how this transaction differs from a DHCP lease renewal.}}<ol><li value="56">On '''centos2''', confirm the IP address assignment using <b><code><span style="color:#3366CC;font-size:1.2em;">ifconfig</span></code></b></li><li>Has the IP Address changed? If so, how has the IP Address been assigned according to the '''dhcpd.conf''' file settings?</li>

'''Answer Part 5 4 observations / questions in your lab log book.'''

== Part 1: Where does the dhcp server store a record of leased addresses?Obtaining Leased Address Infomation=={|width="40%" align="right" |- valign="top"

|{{Admon/note | Use your centos2 and centos3 VMs Purpose of dhcpd.leases File | Complete dhcpd records address leases in this file. If the service is restarted it reads in the following steps on your centos2 file to know which addresses are currently leased and centos3 VMsfor how long.}}

|} # Remain in your '''centos2''' and '''centos3''' VMs for this section.# If your '''centos3 ''' DHCP server successfully issued the proper IP address configuration values to '''centos2''', check the file called :<codebr>'''/var/lib/dhcpd/dhcpd.leases''' in your <u>'''centos3''' VM</codeu># . You should see the similar contents similar to:<br><br>::<prespan style="font-family:courier;">lease 192.168.235.51 {</span>::<span style="font-family:courier;"> starts 3 20105 2015/0307/24 10 17:2857:2534;</span>::<span style="font-family:courier;"> ends 3 20105 2015/0307/24 10 18:17:4834;</span>::<span style="font-family:25courier;"> cltt 3 20105 2015/0307/24 10 17:2857:2534;</span>::<span style="font-family:courier;"> binding state active;</span>::<span style="font-family:courier;"> next binding state free;</span>::<span style="font-family:courier;"> rewind binding state free;</span>::<span style="font-family:courier;"> hardware ethernet 52:54:00:610e:007d:e7a4;</span>}::<span style="font-family:courier;"> client-hostname "centos2";</prespan>{{Admon/note | Purpose of ::<codespan style="font-family:courier;">dhcpd.leases}</codespan> File | dhcpd records address leases in this file. If the service is restarted it reads in the file to know which addresses are currently leased and for how long.}}<ol><li value="3">On the client '''centos2 ''' check the contents of the <codeb>/var/lib/dhclient</codeb> directory. The files in this directory is where the dhclient stores its record of leases.<br><br> '''NOTE:''' If there are no files, then in a shell as root in your centos2 VM issue the command: <b><code><span style="color:#3366CC;font-size:1.2em;">dhclient eth0</span></code></b><br>Then check to see if there is file containing lease information in that directory.<br><br></li>

== Part 2: How can I lease the same address every time? Configuring DHCP server to Continually Lease Same IP Address=={|width="40%" align="right"

{{Admon/note | Use your centos2 and centos3 VMs | Complete the following steps on your centos2 and centos3 VMs.}}- valign="top"

|{{Admon/note | Reserving IP Addresses with DHCP | Even though DHCP gives out IP address dynamically, it also has the ability to reserve an IP address for a certain computer. In this sense it's almost as if the client computer has a static IP even though it uses DHCP to get it. This is useful if you want to be able to put entries in your /etc/hosts file and not have to worry about the entry becoming invalid over time. In Linux we refer to this as supplying a fixed address to a host. Microsoft calls it a reservation.}}

|}# Remain in your '''centos2''' and '''cento3''' VMs for this section.# Make certain that you are located in your '''centos3 ''' virtual machine.# Create a host declaration for '''centos2'''. Make sure you record the correct <code>hardware ethernet</code> setting that corresponds to the MAC address of the interface in '''centos2'''.# Give it the fixed-address '''192.168.235.12{{Admon/tip | Avoiding IP Address Conflicts | 42'''<br><br>'''Note:''' When supplying fixed-address it is important that the address assigned is exclusive of any ranges that have been declared. Otherwise it may be possible for 2 different hosts to receive the same address.}}<br><br><ol><li value="35">Start your service and test the address assignment by releasing your current address on '''centos2 ''' and then requesting a new address. Use the following commands on '''centos2''':</li>

::: <b><code><span style="color:#3366CC;font-size:1.2em;">ifdown eth1</span></code></b>::: <b><code><span style="color:#3366CC;font-size:1.2em;">ifup eth1</span></code></b><ol><li value="46">Confirm that you received the fixed address you were supposed to.</li>

{{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.}} '''Arrange proof of the following on the screen:''' * <ol><li><span style="color:green;font-size:1.5em;">&#x2713;</span> '''centos2''' VM:<blockquote><ul><li>'''ifconfig eth0''' shows IP address '''192.168.235.42'''</li><li>DHCP client lease file</li></ul></blockquote><li><span style="color:green;font-size:1.5em;">&#x2713;</span> '''centos3''' VM:<blockquote><ul><li>DHCP server log file showing a lease occuring* </li><li>DHCP server configuration file showing subnet and host declaration* </li><li>DHCP server lease file* DHCP client lease file</li></ul></blockquote></li><li><span style="color:green;font-size:1.5em;">&#x2713;</span> '''Lab8''' log-book filled out.</li></ol>

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