Lecture

Networking II Lesson Plan Week 8 Addendum


Dynamic Host Configuration Protocol


DHCP Overview


DHCP is used to automatically configure network clients with various networking settings.

DHCP is used by default on Windows machines. The students can view the network settings assigned by DHCP using the ipconfig utility.



Leasing an IP Address


A client is not given an IP address…it merely leases it.

Students mainly need to understand the four-packet process that is necessary for the leasing of an IP address from a DHCP server.

The packets are referred to in the text as: DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, and DHCPACK.







Renewing an IP Address


There are two different types of leases: permanent and timed.

Administrators should use timed leases in most cases as it facilitates IP addressing configuration changes. Timed leases will therefore ease administration tasks.

Students may need to be reminded that a client computer does not attempt to renew its lease after it has expired. A client machine attempts to renew its lease after 50% of the lease time has expired. This helps prevent network problems

The renewal process only requires two packets to complete. Therefore, it requires less traffic to renew a lease than it does to request a lease.





Installing and Authorizing the DHCP Service


  1. A DHCP service must both be installed and authorized before becoming fully functional.

  2. Students should understand that unauthorized DHCP servers could potentially wreak havoc in a networking setting. Therefore, any DHCP service installed must be authorized by a user with sufficient administration privileges.


Installing the DHCP Service


  1. Installing the DHCP service is done in the same way as any other service.

  2. DHCP services are not installed by default on a Windows Server 2003 machine. The service must be installed manually. Students will practice with installing this service in the next activity.


Activity 4-1: Installing DHCP


  1. This is a simple activity that involves the installation of the DHCP service. The activity should pose no problem for the average student.


Authorizing the DHCP Service


  1. Most students will not realize that a DHCP service needs to be authorized before it becomes fully functional. It is probably a safe assumption that most students will have never installed their own DHCP service. This service tends to be provided “behind the scenes” so that the average user has no control or experience with this concept.

  2. Authorization is not difficult provided you have the proper administration rights.



Activity 4-2: Starting an Authorized DHCP Server


  1. This is an activity in starting a service and using the Event Log.

  2. The toughest part of this activity will be for students to find the appropriate record within a potentially lengthy log file. Therefore, make sure students follow instructions carefully.



Activity 4-3: Installing the Active Directory Service


  1. The list of instructions for this activity is somewhat long. However, Microsoft provides an easy to use interface for the installation of the Active Directory Service. Therefore, as long as you make sure they understand the options in the configuration wizard, this will be another easy activity.


Activity 4-4: Starting an Unauthorized DHCP Server


  1. This is an activity in finding records in the System Log.


Activity 4-5: Authorizing a DHCP Server


  1. From the previous activity, students learned of what is recorded within the System Log whenever an unauthorized DHCP server is started. In this activity, students will fix the problem by activating the service.

  2. The instructions for this activity are easy. The only difficulty students could potentially have is if they attempt this activity without the proper administration privileges.


Configuring DHCP Scopes


  1. DHCP configuration can be accomplished via the provided snap-in or through a command line utility called NETSH.

  2. The snap-in is an easy way to configure DHCP. However, have students practice using the NETSH command as it might save configuration time in certain situations.

  3. Scope may sound like a complicated topic for some students. However, it is just a fancy word for the range of IP addresses that a DHCP server is allowed to hand out.

  4. There are two different ways to define scope. One way is to allow all available addresses minus the statically assigned addresses. The other method is to use a range of addresses not already assigned for use in static situations.




Teaching Tip

Have students try to think of situations in which one of the two methods of defining scopes may be better than the other. Include advantages or disadvantages for each method. These considerations may be useful later in a real networking situation.



Activity 4-6: Creating a Scope


  1. In this activity, students will be setting up a scope on their new DHCP server so that it can assign IP addresses to client machines. The instruction list is a little long but easy to follow.





Activity 4-7: Activating and Testing a Scope


  1. This activity is meant to be performed in a group. One person will run the DHCP server while the other runs the client machine.

  2. Have partners switch roles and re-perform the activity.




Teaching Tip

If this activity works, it should not take long to complete. However, troubleshooting may add significant time to this activity. Anytime two computers must communicate via a network, make sure students realize that there always exists the possibility of communication problems between the machines. There are many variables relating to configuration and networking connection complications that may have to be resolved before the activity can be accomplished.



Superscopes


  1. A superscope is used to combine multiple scopes. The concept is simple. However, the reasons for superscoping may not be clear to students.

  2. A company may start with a single class C network and grow to eventually require two class C networks. In order to keep the DHCP server from offering leases from both scopes, a superscope is configured so that only a single lease can be offered.

  3. This is a tricky concept. Make sure students fully understand how a superscope is useful in some networking situations.


Activity 4-8: Configuring a Superscope


  1. This activity involves creating two scopes. First, students should create a normal scope. Then, students will create a superscope encompassing the two previously created scopes.

  2. Everything the student needs to complete this activity can be found in the DHCP snap-in.


Activity 4-9: Deleting a Superscope


  1. This activity is easy. Just remind students to delete only the superscope and not the scopes within it.


Multicast Scopes


  1. Multicast scopes deliver multicast addresses over to applications that request them.

  2. Although this is sometimes used, students must understand that such situations are very rare. Most applications that use multicasts are hard coded with the required addresses and do not need a DHCP server to issue an address.



Activity 4-10: Creating a Multicast Scope


  1. This activity is similar to a previous activity where a student was required to create a regular scope. The only difference in this activity is the fact that students must specify that they are creating a multicast scope.

  2. Even though it is important that students know how to do this, it should be noted that it is rare for client machines to request multicast addresses from DHCP servers.


Activity 4-11: Deleting a Multicast Scope


  1. This activity is self explanatory. The instructions are probably not even necessary.


Creating DHCP Reservations


  1. A reservation is used to assign a specific IP address to a client machine. The reservation is made based on the MAC address of the client machine.

  2. Explain that a reservation is sometimes more convenient to assign a fixed IP address than is using a static configuration on the client side.

  3. Reservations are also useful for machines connected to firewalls as the firewall rules can be configured based upon an IP address. Since an IP address is reserved for a certain machine, the firewall rules are ensured to apply to the correct machine.

  4. Explain the potential problems of reservations. One potential inconvenience is that the reservation must be reconfigured if the network adapter of the client machine is changed.


Activity 4-12: Creating and Testing a Reservation


  1. Students should be instructed to pair up for this activity.

  2. One student will be responsible for configuring the client while the other will be configuring the server.

  3. As with any other activity that involves required communication between two machines, allow enough time for troubleshooting problems.

  4. The point of this activity will be for students to reserve an IP address for a specific client machine.


Configuring DHCP Options


  1. Although handing out IP addresses is perhaps the most important job of the DHCP server, other configurations are handed out by the server as well.

  2. Students should know that they can configure the DHCP server to hand out information such as default gateway, DNS server, WINS server, and others.


Activity 4-13: Setting Server Options


  1. This activity involves configuring the DHCP server with the DNS option. This is an easy activity to perform. However, make sure students know why they may need to do this.



Activity 4-14: Setting Scope Options


  1. In this activity, students set up the DHCP server to provide default gateway information. This activity will not take long.


Activity 4-15: Testing Server & Scope Options


  1. This activity is best done in groups.

  2. In this activity, one person will activate the DHCP scope while the other tests to see if a client machine retrieves the configuration settings entered in previous activities.

  3. Allow troubleshooting time since this activity involves computer to computer communication.


Vendor and User Classes


  1. It is likely that students have not heard of these topics. Therefore, it may be necessary to spend a little more time discussing them and how they are useful.

  2. Vendor classes are operating system based.

  3. User classes are either connection based or administrator based.

  4. The classes are used to specify specific options to client machines.


Configuring a DHCP Relay


  1. DHCP packets are all broadcasting packets. Therefore, students should realize that these packets cannot travel across routers.

  2. In most practical situations, routers will exist on a network. In addition, a single DHCP server will be desired even in the presence of this router.

  3. Students should become familiar with the concept of a DHCP relay. This relay picks up client lease requests and forwards them to the appropriate DHCP server. The relay also transmits the reply from the DHCP server back to the client machine.

  4. Make sure it is very clear that one should not configure a DHCP server to also act as a relay. To do so will result in the machine exhibiting erratic behavior.

  5. If students wonder how the relay solves the router problem, explain that the relay listens for client requests and forwards them to the server as a unicast communication. Unicast communications can travel across routers as they are not broadcasts.


Activity 4-16: Configuring a DHCP Relay


  1. This activity is a little longer than most. However, recommend that students carry out this activity as configuring DHCP relays can be very useful in practical situations.

  2. Make sure students uninstall the DHCP service from this machine before configuring it as a relay. This will help remind students that a machine should never be both a DHCP server and relay.



Additional Projects


  1. You have a network of computers connected through a router. As the network administrator, you are assigned the task of providing DHCP service to the machines. How would you go about providing such service to these computers?


  1. Suppose that it is required to set specific options to machines running specific operating systems on the network. What is the easiest way to do this?


Solutions to Additional Projects


  1. Service should be provided through the use of DHCP relays. Multiple DHCP servers can complicate a network. Therefore, configure a single DHCP server along with relay machines to intercept client requests. The relays will make sure that the DHCP server receives requests and is able to service those requests regardless of routers in between.


  1. If a certain set of options are required for a certain operating system, one should definitely utilize vendor classes. Windows Server 2003 allows separate configurations for clients within the same scope having different vendor classes.










Managing and Monitoring DHCP


Teaching Tips


Backing Up and Restoring DHCP Databases


  1. Like any other database, it should come as no surprise that the DHCP database can be backed up.

  2. Students need to learn from this section that:

    1. The DHCP database can be backed up.

    2. The transaction log files have special names.

    3. The database is automatically backed up every hour by default.

  3. Stress to students that in order to modify the backup interval, they must edit the registry entry in Windows. Be careful when making any changes to the Windows registry.


Activity 5-1: Installing and Authorizing DHCP


  1. This activity involves the installation and authorization of a DHCP service similar to that already performed in Chapter 4 activities.

  2. Students need to: install the service, authorize the service, and add/activate an appropriate scope.

  3. Make sure that students follow this activity step-by-step in order to ensure that everything is properly configured for later activities.


Activity 5-2: Backing up a DHCP Database


  1. In this activity, students will learn how to back up a DHCP database.

  2. This is an easy activity. Students will use the DHCP snap-in to initiate the backup and then manually verify that the backup files were written.


Activity 5-3: Changing the Default Location of the DHCP Database


  1. This is a simple activity where the system administrator will choose a different location to store DHCP related information.

  2. Everything for this activity can be initiated from the DHCP snap-in.


Activity 5-4: Restoring a DHCP Database


  1. This activity is obviously the opposite of the activity in which a backup was created.

  2. Again, this is just another exercise in using the DHCP snap-in.


Maintaining the DHCP Database


  1. The main idea of this section is that, as the DHCP database grows, it may sometimes need maintenance due to inconsistencies that appear. The service can be repaired by either reconciling the scope or repairing the DHCP database itself.


Reconciling Scopes


  1. The term reconciling will probably not be familiar to the average student as it applies to the DHCP database.

  2. Explain that reconciling will fix such errors as:

    1. discrepancies between detailed and summary information in the database

    2. information is not appearing properly in the DHCP snap-in

  3. The database may need to be reconciled after restoring the DHCP database.


Activity 5-5: Reconciling a Scope


  1. In this activity, students will actually be reconciling a scope.

  2. This is an easy activity that involves the DHCP snap-in.

  3. The toughest part in reconciling a scope is knowing when to perform the task as opposed to how to perform it.


Repairing the DHCP Database


  1. The moral of this section is that the potential for database problems increases as the database size increases.

  2. A corrupted database may be directly repaired using the jetpack command-line utility.

  3. Make sure you explain the parameters used with this command.


Activity 5-6: Running the Jetpack Utility


  1. In this activity, students will issue the command provided in the text so as to practice repairing a corrupted DHCP database.


Viewing DHCP Statistics


  1. Students need to realize, for convenience, that Windows Server 2003 DHCP services automatically keeps statistical information about itself.

  2. Explain that the statistics can be viewed from the DHCP snap-in or from the performance snap-in.




Teaching Tip

The performance snap-in is an underrated little utility that can be very useful in situations for which you want to quickly view the overall health of a server. It is much faster to configure and subsequently use this snap-in to view the server’s health than it is to go to individual snap-ins.


DHCP Audit Logging


  1. A DHCP audit log merely keeps track of DHCP server activity.

  2. The log keeps track of, by default, the last seven days of activity.

  3. The DHCP audit log uses a number of event IDs. Students should probably have a table of such IDs when trying to view an audit log in order to gain a better understanding of what is going on.


Activity 5-7: Viewing an Audit Log


  1. Students will be using notepad to view the DHCP audit log.


Conflict Detection


  1. An important fact that many may not realize is that one may still statically configure their computer even in the presence of a DHCP server. The DHCP server can do nothing to prevent this from occurring.

  2. Conflict detection merely refers to the ability of a DHCP server to avoid IP addressing conflicts. Windows Server 2003 tries to avoid such conflicts by trying to ping an IP address before handing it out someone else.

  3. As with most everything else in this operating system, the number of pings the server will try before assuming the address is free is configurable by the network administrator.


Activity 5-8: Configuring Conflict Detection


  1. In this activity, students will be setting the number of ping attempts to avoid IP conflicts to two.

  2. This activity involves the DHCP snap-in.


Configuring DHCP Bindings


  1. The main idea of this section is that you can specify the DHCP service to operate through a particular network adapter as required.


Activity 5-9: Setting Bindings for DHCP


  1. Again, this is a quick activity that involves binding the DHCP service through the DHCP snap-in.


Viewing DHCP Events in Event Viewer


  1. Make sure students understand that DHCP events can be viewed using the Event Viewer provided with Windows.


Activity 5-10: Viewing DHCP Events in Event Viewer


  1. This activity will involve students in using the Event View for viewing DHCP events.

  2. This activity will certainly pose no challenge to the average student.


DHCP Troubleshooting


  1. DHCP seldom has problems.

  2. The text offers a number of tips that can be used in order to try to troubleshoot a network using DHCP.

  3. Review each of the problems listed in the text. Learning how to troubleshoot via a textbook is probably not going to be very effective. Students will learn how to troubleshoot through experience more than anything else.

  4. The information in the text should provide students with a place to begin their troubleshooting efforts in the case that they are experiencing one of the basic problems listed in this section.



Activity 5-11: Remove DHCP


  1. Students will remove the service simply through the Add/Remove Windows Components utility.