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

|- valign="top"|width="8%" | <u>'''D'''</u>iscovery:|width="90%" |The client broadcasts a '''message''' (IP lease request) on a sub-network to '''discover''' available DHCP servers|- valign="top"|width="8%" | <u>'''O'''</u>ffer:|width="90%" |The DHCP server receives the request from the client, '''reserves an IP ADDRESS''' for the client and sends a '''DHCPOFFER'''|- valign="top"|width="8%" | <u>'''R'''</u>equest:|width="9%" |The DHCP server broadcasts a message '''request for acceptance''', but also notifies other DHCP server|- valign="top"|width="8%" | <u>'''A'''</u>cknowledgement:|width="90%" |The client sends a '''message of acceptance to the server'''. In turn, the client receives from the server a '''packet of information''' containing the lease duration and other configuration information|}<br><br>== Part 1: Installation of a DHCP=={| width="40%" align="right" cellpadding="10"|- valign="top"|{{Admon/important note| Update VM Backups and Yum Updates|Before proceeding with this lab make certain that you have backed-up from lab7, and then perform a '''yum update''' on all machines (including your systems VMs)| It }}|}# Perform this section in your '''centos3''' VM.<br><br>The version of DHCP server that comes with CentOS is maintained and distributed by the Internet Software Consortium (http://www.isc.org). The source package that you can download from ISC includes not only the DHCP server, but also a DHCP client and a DHCP relay agent. CentOS separates it into two RPM packages: the DHCP client package and the DHCP server package. The DHCP client package is advisable installed by default by the workstation installation.<br><br># To check that you have <b>dhclient</b> installed, enter the command:#:: <b><code><span style="color:#3366CC;font-size:1.2em;">rpm -q dhclient</span></code></b># 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 <b>dhclient</b> package if it was not installed.# Issue the following command to perform a install the dhcp server package: <b><code><span style="color:#3366CC;font-size:1.2em;">yum updateinstall dhcp</span></code> on your host and </b># Enter the command to list all 3 VMthe files installed from the DHCP server package by issuing the command: <b><code><span style="color:#3366CC;font-size:1.2em;">rpm -qla dhcp</span></code></b># What file appears to be a sample (example) configuration file for dhcpd.conf?# Copy the '''dhcpd.conf.example''' file to the '''/etc/dhcp''' directory making sure it is named: '''s/etc/dhcp/dhcpd.}}conf'''

{{Admon'''Answer Part 1 observations /important questions in your lab log book.'''  == Part 2: Configuring the DHCP Server== [[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>  '''Answer Part 2 observations / questions in your lab log book.}}'''

# Perform this section in your '''centos3''' VM.# To check that you have <code>dhclient</code> installed, enter the command== Part 3:Configuring DHCP Server for Static IP Addresses==:: <code>rpm -q dhclient</code><ol><li value{|width="240%"> If the package is not installed, you will get the message align="package dhclient is not installedright", 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>

=== Investigation 2: What configuration options and directives need to be set in dhcpd.conf?===|{{Admon/note important | Use your centos3 VM Recall Secure SSH Connection Method from Lab7 | Complete Do not forget that you made ssh more secure in the previous lab. Therefore, you will need to use the following steps on same command in lab7 to securely connect to your centos3 VM.}}

 # Remain in your '''centos3''' VM for this section.# Study the man pages of <code>dhcpd<Edit '''/code>, <code>dhcpd.conf<etc/code>, <code>dhcp-options</code>, and <code>dhcpd.leases</code> conf''' for a second time.# View this file for existing subnet declarations. Note the syntax and make notes in your log book. In particular, look up the meaning directive for '''range''' and possible valuethe option for '''routers''' (sgateway).# Now, if any, add a new subnet delcaration for the following configuration options::your virtual network:* <codebr>broadcast-address</codebr>The network address is::* <code>default-lease-time<'''192.168.235.0/code>::* 255.255.255.0'''<codebr>max-lease-time</code> (How is this different range of host addresses should be from : '''51 to 60'''<codebr>default-lease-time</code>?gateway (routers)for the virtual network is::* '''192.168.235.1'''<codebr>domain-name</codebr>::* # Save your editing session, and exit the text editor.<codeol>domain-name-servers</codeli value="6">:Open another terminal window (ssh into centos3 from the centos host as user root) and issue the following command:* <codebr>fixed-address</codeb>::* <code>group</code>span style="color:#3366CC;font-size:* <code1.2em;">hardwaretail -f /var/log/messages</codespan>::* </code>host</codeb>::* <codebr>host-name<br>(This will show you the last lines of '''/var/code>::* <code>range<log/code>::* messages''' continue to display new lines as they are added to the log.)<code>routers</codebr>::* <codebr>subnet</codeli>::* <codeli>subnet-maskIn your original terminal prompt attempt to start the '''dhcpd''' service.</codeli><ol><li value="2"> Study You should see new lines being added to the sample <code>dhcpd.conf</code> messages file to see examples of how these options are used.</li>

=== Investigation 3: How do I configure dhcpd settings to be applied to all subnets?===|{{Admon/note tip | Use Troubleshooting Tip: | Troubleshooting produces the best results when you are methodical in your centos3 VM | Complete 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 following steps on first error try to start your centos3 VMservice and if it fails check the log again. Fix one error at a time.}}

# Edit |}<codeol>/etc/dhcp/dhcpd.conf</codeli value="9"> and examine If the top section of '''dhcpd''' service fails to start any error messages will be logged in the messages file.# Make Read the following changes errors and attempt to the global settings:::* fix your configuration file.<code/li>domain-name</codeli> should be set to If the '''ops235.orgdhcpd'''::* service starts successfully you should see success messages in the log. <code/li>domain-name-servers</codeli> should be set to If your '''192.168.235.1dhcpd'''::* service starts successfully, try to generate errors by editing the configuration file and introduce an error by removing a semicolon or closing curly bracket.<code/li>default-lease-time</codeli> should be set to Restart your '''20 minutesdhcpd'''service and observe the error messages generated. This is good practice to learn how to trouble-shoot and solve dhcpd errors.</li>::* <codeli>max-lease-timeMake certain that you have corrected those errors, and that your dhcpd service works properly.</codeli> should be set 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 '''1 hourchkconfig'''<ol><li value="3">Save and exit your editing sessioncommand to enable the dhcpd service so it started automatically upon boot-up.</li>

=== Investigation 4: How do I configure dhcpd to provide IP configuration to my virtual network?==={{Admon'''Answer Part 3 observations /note | Use questions in your centos3 VM | Complete the following steps on your centos3 VMlab log book.}}'''

<ol><li value== Part 4: How do I test my dhcpd service on my virtual network?=={|width="40%" align="right" |- valign="5top">Open another  |{{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.}} |}# Use your '''centos2''' and '''centos3''' VMs for this section.# On your '''centos3''' terminal window (via ssh into centos3 from the centos host as user rootyour c7host machine) and issue make sure that the following command:::: <codebr><b>tail -f /var/log/messages</codeb>is running.<li>This will show you # On your '''centos2''' VM, change the last 10 lines 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)<codebr>([http://zenit.senecac.on.ca/varwiki/logindex.php/messagesOPS235_Lab_6_-_CentOS7#Part_2:_Configuring_VM_Network_Setup_Graphically_.28system-config-network.29 Refer to Lab6, Investigation1, Part2]).<br></codebr> continue to display new lines as they Note: if you are added configuring via command line, make certain to restart the lognetwork for centos2.# Logout and restart your '''centos2''' VM.</li><li>In # Observe the messages that get logged from the tail -f command as your original terminal prompt attempt centos2 VM starts. You should see output similar to start the following:<codebr><br>dhcpd::</codespan style="font-family:courier;"> service.Mar 24 13:28:24 centos3 dhcpd: DHCPDISCOVER from 52:54:00:61:00:e7 via eth2</lispan>::<lispan style="font-family:courier;">You should see new lines being added Mar 24 13:28:25 centos3 dhcpd: DHCPOFFER on 192.168.235.51 to the messages file.52:54:00:61:00:e7 via eth2</lispan>::<li>If the <codespan style="font-family:courier;">Mar 24 13:28:25 centos3 dhcpd</code> service fails to start any error messages will be logged in the messages file: DHCPREQUEST for 192.168.235.51 (192.168. Read the errors and attempt to fix your configuration file235.13) from 52:54:00:61:00:e7 via eth2</lispan>::<lispan 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>If the <codebr>dhcpd</codespan> service starts successfully you should see success messages in the log. </liol><livalue="6">If your On '''centos2''', confirm the IP address assignment using <codeb>dhcpd</code> service starts successfully, try to generate errors by editing the configuration file and introduce an error by removing a semicolon or closing curly bracket<span style="color:#3366CC;font-size:1.2em;">ifconfig</lispan><li>Restart your </code>dhcpd</codeb> service and observe the error messages generated. This is good practice to learn how to trouble-shoot and solve dhcpd errors.</li><li>Make certain that you have corrected those errorsHas the IP Address changed? If so, and that your how has the IP Address been assigned according to the '''dhcpd service works properly.conf''' file settings?</li>

=== Investigation 5INVESTIGATION 2: How do I test my dhcpd service on my virtual network?==OBTAINING LEASE & LEASE PERMANENT IP ADDRESS INFORMATION=

# On a centos3 terminal window make sure that the command <code>tail -f /var/log/messages</code> is running.# On your centos2 VM, change the configuration of '''eth0''' (or your interface name) to receive dynamic address configuration.# Save your changes and restart the <code>NetworkManager</code> service.# Observe the messages that get logged. You should see output similar to the following== Part 1:<pre >Mar 24 13:28:24 centos3 dhcpd: DHCPDISCOVER from 52:54:00:61:00:e7 via eth2Mar 24 13:28:25 centos3 dhcpd: DHCPOFFER on 192.168.235.51 to 52:54:00:61:00:e7 via eth2Mar 24 13:28:25 centos3 dhcpd: DHCPREQUEST for 192.168.235.51 (192.168.235.13) from 52:54:00:61:00:e7 via eth2Mar 24 13:28:25 centos3 dhcpd: DHCPACK on 192.168.235.51 to 52:54:00:61:00:e7 via eth2</pre>Obtaining Leased Address Infomation=={{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 valuewidth="40%" align="5right">On centos2, confirm the IP address assignment using <code>ifconfig</code></li></ol>

{{Admon/note | Use your centos2 and centos3 VMs | Complete the following steps on # Remain in your '''centos2 ''' and '''centos3 ''' VMsfor 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>

'''Answer the Investigation 6 Part 1 observations / questions in your lab log book.'''

==Part 2: Configuring DHCP server to Continually Lease Same IP Address= Investigation 7: How can I lease the same address every time? ={|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>

 '''Answer the Investigation 7 Part 2 observations / questions in your lab log 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.}} '''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 ==