= LAB PREPARATION = ===Overview==={| width="40%" align="right" cellpadding="10"|- valign="top"|[[Image:ip.png|thumb|right|250px|Some computer networks (such as computer labs) configure their workstations for '''static IP addresses for security and to provide other interesting features such as WOL'''.]]|[[Image:wifi.png|thumb|right|155px|'''Hot-spots''' offer the ability for users to connect to the Internet via their mobile devices. '''Hybrid solutions''' combine DHCP and fixed IP Address. ]]|}There are various ways in which computers can be networked together. Some computer networks (such as computer labs) configure their workstations for '''static IP addresses for security and to provide other interesting features such as WOL''' (Wake Up on Lan) which allows a signal from a computer system to remotely start all or specified workstations within the lab. '''Hot-spots (such as cafes or airport lounges) offer the ability for users to connect to the Internet (via DHCP) from their mobile devices''' (notebooks, netbooks, tablets, or smart phones). Finally, there are '''hybrid solutions that may offer both fixed IP address (computer workstations) and allow for wireless connections (via DHCP) to a mobile devices''' (like at your Seneca computer labs). In lab6, you learned to connect your VMs to a VPN using a fixed IP Address. In this final lab, you will learn to set-up a '''DHCP server''' to automatically assign IP Addresses upon connection requests. <u>Main Objectives</u> * To install, configure, and test ISC's DHCP Server.* To obtain log information from DHCP server including lease address information.* To lease the same IP address every-time from VM boot-up (instead of having DHCP server randomly assign IP address). ===Minimum Required Materials=== {|cellpadding="15" width="20%" |- valign="top" |width="20%" |[[Image:ubs-key.png|thumb|left|85px|<b>USB key</b><br>(for backups)]] |width="20%" |[[Image:log-book.png|thumb|left|70px|<b>Lab8 Log Book</b>]] |} ===My Toolkit (CLI 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:'''|'''Configuration Files:'''|- valign="top"| *[http://linux.die.net/man/8/dhcpd dhcpd]*[http://man7.org/linux/man-pages/man8/ifconfig.8.html ifconfig]|*[http://man7.org/linux/man-pages/man1/tail.1.html tail]*[http://linux.die.net/man/8/chkconfig chkconfig]|*[https://www.freebsd.org/cgi/man.cgi?query=dhcpd.conf&sektion=5&apropos=0&manpath=FreeBSD+9.0-RELEASE+and+Ports dhcpd.conf]*[http://linux.die.net/man/5/dhcp-options dhcpd-options]*[http://linux.die.net/man/5/dhcpd.leases dhcpd.leases]* [http://www.centos.org/docs/5/html/Deployment_Guide-en-US/s1-dhcp-configuring-server.html Configuring a DHCP Server ]|} =INVESTIGATION 1: INSTALL AND CONFIGURE A DHCP SERVER=[[Image:dora.png|thumb|right|400px|The term '''DORA''' best describes how '''DHCP''' works. ]] This lab will demonstrate setting up a DHCP server. The term '''DHCP''' stands for '''Dynamic Host Configuration Protocol'''. DHCP allows computers (eg. workstations, notebooks, smart-phones) to be automatically configured so that they can communicate over a network. This automatic configuration has gained popularity over the years, especially as the need for detecting and configuring portable computer devices increases. DHCP configuration allows for various setups including: '''Dynamic''', '''Automatic''', and '''Static''' allocation.<br><br>The term '''DORA''' best describes how DHCP Works:<br><br>{|cellpadding="2" width="60%" |- 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/note|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 VMs)|}}|}# Perform this section in your '''centos4''' 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 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 install the dhcp server package: <b><code><span style="color:#3366CC;font-size:1.2em;">yum install dhcp</span></code></b># Enter the command to list all the 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: '''/etc/dhcp/dhcpd.conf''' '''Answer Part 1 observations / questions in your lab log book.''' == Part 2: Configuring the DHCP Server== [[Image:dhcp-config.png|thumb|right|500px|The '''dhcpd.config''' file allows the Linux system administrator to customize the DCHP 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, the '''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!''' ]] # Remain in your '''centos4''' VM for this section.# Click on the following link to access the online manual page for the following DHCP items to gain an understanding: <ul><li>[http://linux.die.net/man/8/dhcpd dhcpd]</li><li>[https://www.freebsd.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.leases]<br><br></li></ul># Study the sample '''dhcpd.conf''' file to see examples of how these options are used.# Edit '''/etc/dhcp/dhcpd.conf''' and examine the top section of the file.# Look for the comment: '''"option definitions common to all supported networks"'''# Below that comment change the existing global options to reflect the newer values shown below:<br><br><br>'''domain-name''' '''"ops235.org";'''<br>'''domain-name-servers''' '''192.168.235.1;'''<br><br>'''default-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.''' == Part 3: Configuring DHCP Server for Static IP Addresses=={|width="40%" align="right" |- valign="top" |{{Admon/important | Recall Secure SSH Connection Method from Lab7 | Do not forget that you made ssh more secure in the previous lab. Therefore, you will need to use the same command in lab7 to securely connect to your VM.}} |} # Remain in your '''centos4''' VM for this section.# Edit '''/etc/dhcp/dhcpd.conf''' for a second time.# View this file for existing subnet declarations. Note the syntax and the directive for '''range''' and the option for '''routers''' (gateway).# Now, add a new subnet delcaration for your virtual network:<br><br>The network address is: '''192.168.235.0/255.255.255.0'''<br>range of host addresses should be 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 centos4 from the centos host as user root) and issue the following command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">tail -f /var/log/messages</span></code></b><br><br>(This will show you the last lines of '''/var/log/messages''' continue to display new lines as they are added to the log.)<br><br></li><li>In your original terminal prompt attempt to start the '''dhcpd''' service.</li><li>You should see new lines being added to the messages file.</li></ol>{|width="40%" align="right" |- valign="top" |{{Admon/tip | Troubleshooting Tip: | Troubleshooting produces the best results when you are methodical in your 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 again. Fix one error at a time.}} |}<ol><li value="9">If the '''dhcpd''' service fails to 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 generate errors by editing the configuration file and introduce an error by removing a semicolon or closing curly bracket.</li><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.</li><li>Make certain that you have corrected those errors, and that your 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 dhcpd service so it started automatically upon boot-up.</li></ol> '''Answer Part 3 observations / questions in your lab log book.''' == Part 4: How do I test my dhcpd service on my virtual network?=={|width="40%" align="right" |- valign="top" |{{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 '''centos3''' and '''centos4''' VMs for this section.# On your '''centos4''' terminal window (via ssh from your centos1 machine) make sure that the command<br><b>tail -f /var/log/messages</b> is running.# On your '''centos3''' 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#Part_2:_Configuring_VM_Network_Setup_Graphically_.28system-config-network.29 Refer to Lab6, Investigation1, Part2]).<br><br>Note: if you are configuring via command line, make certain to restart the network for centos3.# Logout and restart your '''centos3''' VM.# Observe the messages that get logged from the tail -f command as your centos3 VM starts. You should see output similar to the following:<br><br>::<span style="font-family:courier;">Mar 24 13:28:24 centos4 dhcpd: DHCPDISCOVER from 52:54:00:61:00:e7 via eth2</span>::<span style="font-family:courier;">Mar 24 13:28:25 centos4 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 centos4 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 centos4 dhcpd: DHCPACK on 192.168.235.51 to 52:54:00:61:00:e7 via eth2<br><br></span><ol><li value="6">On '''centos3''', 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></ol> '''Answer Part 4 observations / questions in your lab log book.''' =INVESTIGATION 2: OBTAINING LEASE & LEASE PERMANENT IP ADDRESS INFORMATION= == Part 1: Obtaining Leased Address Infomation=={|width="40%" align="right" |- valign="top" |{{Admon/note | Purpose of dhcpd.leases 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.}} |} # Remain in your '''centos3''' and '''centos4''' VMs for this section.# If your '''centos4''' DHCP server successfully issued the proper IP address configuration values to '''centos3''', check the file called:<br>'''/var/lib/dhcpd/dhcpd.leases''' in your <u>'''centos4''' VM</u>. You should the similar contents:<br><br>::<span style="font-family:courier;"> lease 192.168.235.51 {</span>::<span style="font-family:courier;"> starts 5 2015/07/10 17:57:34;</span>::<span style="font-family:courier;"> ends 5 2015/07/10 18:17:34;</span>::<span style="font-family:courier;"> cltt 5 2015/07/10 17:57:34;</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 52:54:00:0e:7d:a4;</span>::<span style="font-family:courier;"> client-hostname "centos3";</span>::<span style="font-family:courier;"> }</span><ol><li value="3">On the client '''centos3''' check the contents of the <b>/var/lib/dhclient</b> 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 centos3 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></ol> '''Answer Part 1 observations / questions in your lab log book.''' == Part 2: Configuring DHCP server to Continually Lease Same IP Address=={|width="40%" align="right" |- 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 '''centos3''' and '''cento3''' VMs for this section.# Make certain that you are located in your '''centos4''' virtual machine.# Create a host declaration for '''centos3'''. Make sure you record the correct <code>hardware ethernet</code> setting that corresponds to the MAC address of the interface in '''centos3'''.# Give it the fixed-address '''192.168.235.42'''<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="5">Start your service and test the address assignment by releasing your current address on '''centos3''' and then requesting a new address. Use the following commands on '''centos3''':</li></ol>::: <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="6">Confirm that you received the fixed address you were supposed to.</li></ol> '''Answer Part 2 observations / questions in your lab log book.''' = LAB 8 SIGN-OFF (SHOW INSTRUCTOR) ={{Admon/important|Time for a new backup!|If you have successfully completed this lab, make a new backup of your virtual machines as well as your host machine.}} ===Download and Run Lab8 Checking Script & Show Lab8 Work=== '''Perform the Following Steps:''' # Issue the Linux command: <b><code><span style="color:#3366CC;font-size:1.2em;">wget http://matrix.senecac.on.ca/~murray.saul/ops235/lab8-check.bash</span></code></b># Give the '''lab8-check.bash''' file execute permissions (for the file owner).# Run the shell script and if any warnings, make fixes and re-run shell script until you receive "congratulations" message.#Arrange proof of the following on the screen:<br><blockquote><span style="color:green;font-size:1.5em;">✓</span> '''centos3''' VM:<blockquote><ul><li>'''ifconfig eth0''' shows IP address '''192.168.235.42'''</li><li>DHCP client lease file</li></ul></blockquote><span style="color:green;font-size:1.5em;">✓</span> '''centos4''' 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</li></ul></blockquote><span style="color:green;font-size:1.5em;">✓</span> '''Lab8''' log-book filled out. = Practice For Quizzes, Tests, Midterm & Final Exam = # What protocol and port does dhcp use? # What file is used to configure dhcpd?# Can a dhcp server also be a dhcp client?# What is the difference between max-lease-time and default-lease-time?# What unit of measurement does default-lease-time require?# What dhcp option is used for configuring a default gateway?# What is the parameter range in the DHCP server configuration file used for? # What is the purpose of a dhcp relay agent?# Why might a dhcp relay agent be required? REDIRECT [[Category:OPS235]]
