1. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
Module 4: Configuring and Troubleshooting DHCP
Presentation: 60 minutes
Lab: 30 minutes
Module 4: Configuring and Troubleshooting DHCP
This module helps students to configure, manage, and troubleshoot a Dynamic Host Configuration Protocol (DHCP) environment supporting an IPV4 infrastructure.
After completing this module, students will be able to:
Describe the DHCP Server role.
Configure DHCP scopes and options.
Manage a DHCP database.
Monitor and troubleshoot DHCP.
Secure DHCP.
Required materials
To teach this module, you need the Microsoft Office PowerPoint® file 6421A_04.ppt.
Important It is recommended that you use PowerPoint 2002 or a later version to display the slides for this course. If you use PowerPoint Viewer or an earlier version of PowerPoint, all the features of the slides might not be displayed correctly.
Preparation tasks
To prepare for this module:
Read all of the materials for this module.
Practice performing the demonstrations and the lab exercises.
Work through the Module Review and Takeaways section, and determine how you will use this
section to reinforce student learning and promote knowledge transfer to on-the-job performance.
Make sure that students are aware that the Course Companion CD has additional information and resources for the module.

2. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
Module 4: Configuring and Troubleshooting DHCP
Module 4: Configuring and Troubleshooting DHCP
Overview of the DHCP Server Role
Configuring DHCP Scopes and Options
Managing a DHCP Database
Monitoring and Troubleshooting DHCP
Securing DHCP

3. Lesson 1: Overview of the DHCP Server Role
Course 6421A
Lesson 1: Overview of the DHCP Server Role
Module 4: Configuring and Troubleshooting DHCP
Benefits of Using DHCP
New DHCP Features in Windows Server 2008
How DHCP Allocates IP Addresses
How DHCP Lease Generation Works
How DHCP Lease Renewal Works
DHCP Server Authorization
Demonstration: Adding the DHCP Server Role

4. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
Benefits of Using DHCP
Module 4: Configuring and Troubleshooting DHCP
DHCP reduces the complexity and amount of administrative work by using automatic TCP/IP configuration
Define DHCP.
Explain how DHCP reduces the complexity and amount of administrative work by using automatic Transmission Control Protocol/Internet Protocol (TCP/IP) configuration.
Explain the difference between manual and automatic TCP/IP configuration.
Provide examples of how DHCP reduces the complexity and amount of administrative work.
Manual TCP/IP Configuration
Automatic TCP/IP Configuration
IP addresses are entered manually
IP address could be entered incorrectly
Communication and network issues can result
Frequent computer moves increase administrative effort
IP addresses are supplied automatically
Correct configuration information is ensured
Client configuration is updated automatically
A common source of network problems is eliminated

5. New DHCP Features in Windows Server 2008
Course 6421A
New DHCP Features in Windows Server 2008
Module 4: Configuring and Troubleshooting DHCP
New DHCP features include:
The DHCP role on Microsoft Windows® Server 2008 supports several new features:
Supports DHCPv6 stateful and stateless configuration for configuring clients in an IPv6 environment.
Helps isolate potentially malware-infected computers from the corporate network via Network Access Protection (NAP) with DHCP.
Enables DHCP installation as a role on a Windows Server® 2008 Server Core installation.
References
DHCP Server
The DHCPv6 Protocol
Windows Server 2008 Support for DHCPv6
Support for advanced network security configuration using NAP
DHCP on Server Core

6. How DHCP Allocates IP Addresses
Course 6421A
How DHCP Allocates IP Addresses
Module 4: Configuring and Troubleshooting DHCP
DHCP Client2: IP configuration from DHCP server
Non-DHCP Client: Static IP configuration
DHCP allocates IP addresses on a dynamic basis, called a lease. You can set the lease value to unlimited. However, the value typically is not more than a few hours or days.
Ensure that students understand that the two methods for obtaining a lease are to request a new lease or to renew an existing lease.
DHCP uses IP broadcasts to initiate communications. Therefore, DHCP servers are limited to communication within their IP subnet. This means that in many networks, there is a DHCP server for each IP subnet. When this is not feasible, either for cost or management reasons, you can use a DHCP relay agent.
The DHCP relay agent allows DHCP broadcast packets to be relayed into another IP subnet across a router. This makes it possible to maintain a singe DHCP server that services multiple IP subnets. DHCP packets also may be relayed into other subnets using a router that is compatible with RFC 1531.
References
Request for Comments 1531:
Microsoft TechNet: DHCP Resources:
Lease Renewal
Lease Generation
DHCP Server
DHCP
Database
DHCP Client1: IP configuration from DHCP server
IP Address1: Leased to DHCP Client1
IP Address2: Leased to DHCP Client2
IP Address3: Available to be leased

7. How DHCP Lease Generation Works
Course 6421A
How DHCP Lease Generation Works
Module 4: Configuring and Troubleshooting DHCP
DHCP client broadcasts a DHCPDISCOVER packet 1
DHCP servers broadcast a DHCPOFFER packet 2
DHCP client broadcasts a DHCPREQUEST packet 3
DHCP Server1 broadcasts a DHCPACK packet 4
DHCP Client
DHCP Server1
DHCP Server2
DHCP Server2
This text for this Topic page does not represent the full process.
This Topic should be taught using the slide. Inform the students that the text in their workbook does not represent the entire process. Describe the process using the additional detail included on the student's Companion CD (and listed here):
1. The DHCP client broadcasts a DHCPDISCOVER packet. This is a message that is broadcast to every computer in the subnet. The only computer that will respond is the computer that has the DHCP server role or, if the computer is running the DHCP server agent. In the latter case, the agent will forward the message to the DHCP server with which it is configured.
2. Any DHCP Server in the subnet will respond by broadcasting a DHCPOFFER packet. This packet will provide the client with a potential address.
3. The client receives the DHCPOFFER packet. It may receive packets from multiple servers. If the client receives offers from more than one server, it usually will choose the server that made the fastest response to its DHCPDISCOVER. This typically is the DHCP server closest to the client. The client then will broadcast a DHCPREQUEST. The DHCPREQUEST contains a server identifier. This informs the DHCP servers that receive the broadcast which server the client has chosen to accept the DHCPOFFER.
4. The DHCP servers receive the DHCPREQUEST. Those servers that the DHCPREQUEST message does not accept use the message as notification that the client has declined that server’s offer. The chosen server stores the IP address client information in the DHCP database and responds with a DHCPACK message. If for some reason the DHCP server cannot provide the address that was offered in the initial DHCPOFFER, the DHCP server will send a DHCPNAK message.
Explain that DHCP uses a four-step process to lease IP addressing information to DHCP clients. Describe the DHCP lease-generation process by referring to the slide’s illustration.
It is important that students understand this process. Run through the demonstration as many times as necessary.
References
MOC 2277C: Module 1
Microsoft TechNet: How DHCP Technology Works:
DHCP Server1
DHCP Client
DHCP client broadcasts a DHCPDISCOVER packet 1
DHCP servers broadcast a DHCPOFFER packet 2
DHCP client broadcasts a DHCPREQUEST packet 3
DHCP Server1 broadcasts a DHCPACK packet 4

8. How DHCP Lease Renewal Works
Course 6421A
How DHCP Lease Renewal Works
Module 4: Configuring and Troubleshooting DHCP
DHCP Client
DHCP Server1
DHCP Server2
DHCP client sends a DHCPREQUEST packet 1
DHCP Server1 sends a DHCPACK packet 2
50% of lease duration has expired
DHCP Client
DHCP Server1
DHCP Server2
DHCP Renewal occurs when 50% of lease duration has expired.
Describe the DHCP lease-renewal process by referring to the slide’s illustration.
References
MOC 2277C: Module 1
Microsoft TechNet: How DHCP Technology Works:
100% of lease duration has expired
50% of lease duration has expired
87.5% of lease duration has expired
If the client fails to renew its lease, after 50% of the lease duration has expired, then the DHCP lease renewal process will begin again after 87.5% of the lease duration has expired
If the client fails to renew it’s lease, after 87.5% of the lease has expired, then the DHCP lease generation process starts over again with a DHCP client broadcasting a DHCPDISCOVER
DHCP Client sends a DHCPREQUEST packet 1
DHCP Server1 sends a DHCPACK packet 2

9. DHCP Server Authorization
Course 6421A
DHCP Server Authorization
Module 4: Configuring and Troubleshooting DHCP
DHCP authorization is the process of registering the DHCP Server service in the Active Directory domain to support DHCP clients
DHCP Server1 checks with the domain controller to obtain a list of authorized DHCP servers
If DHCP Server1 finds its IP address on the list, the service starts and supports DHCP clients
Students should know and understand the importance of DHCP authorization. A rogue DHCP server can cause problems in a network. Incorrectly configured clients can cause numerous issues. When you install a DHCP role in a domain, an Enterprise Administrator must authorize it because several domains can exist in the same IP subnet.
Although it is not recommended, you can use a stand-alone server as a DHCP server, provided that it is not on a subnet with any authorized DHCP servers. When a stand-alone DHCP server detects an authorized server on the same subnet, it automatically stops leasing IP addresses to DHCP clients.
It also is important to note that other network devices may run DHCP servers. These devices do not comply with the notion of being authorized, and therefore they may cause issues in a networked environment.
References
Microsoft TechNet: DHCP Resources:
Microsoft TechNet: Networking Collection:
Domain
Controller
Active
Directory
DHCP Client
DHCP Server1
Authorized
Services DHCP requests
DHCP Server2
Unauthorized
Does not service DHCP requests
If DHCP Server2 does not find its IP address on the list, the service does not start and support DHCP clients
DHCP client receives IP address
from authorized DHCP Server1
DHCP Server2 checks with the
domain controller to obtain a list of
authorized DHCP servers

10. Demonstration: Adding the DHCP Server Role
Course 6421A
Demonstration: Adding the DHCP Server Role
Module 4: Configuring and Troubleshooting DHCP
In this demonstration, you will see how to add and authorize the DHCP Server role
Demonstrate how to:
Add the DHCP server role.
Authorize the DHCP Server role.
Demonstration steps:
Open Server Manager, click Roles, click Add Role, click DHCP, and then go through the Installation wizard.
After the DHCP service is installed, open the Firewall applet in Control Panel, click Advanced, and show the class that Server Manager created the necessary exception in the firewall.
Remove the DHCP service, and reboot the server.
Install the DHCP role from the command prompt:
Click Start, and then click Command Prompt.
Type: servermanagercmd -install DHCP -resultPath installResult.xml
The role will install.
Open the installResult.xml file using Notepad.
Information about installing the role is displayed.

11. Lesson 2: Configuring DHCP Scopes and Options
Course 6421A
Lesson 2: Configuring DHCP Scopes and Options
Module 4: Configuring and Troubleshooting DHCP
What Are DHCP Scopes?
What Are Superscopes and Multicast Scopes?
Demonstration: Configuring DHCP Scopes
What Are DHCP Options?
What Are DHCP Class-Level Options?
What Is a DHCP Reservation?
DHCP Sizing and Availability
How DHCP Options Are Applied
Demonstration: Configuring DHCP Options

12. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
What Are DHCP Scopes?
Module 4: Configuring and Troubleshooting DHCP
A scope is a range of IP addresses that are available to be leased
DHCP Server
Describe the purpose of a DHCP scope.
Explain that administrators must create a DHCP scope before leasing IP addresses to a client. A DHCP scope is a range of IP addresses that are available for lease.
Scope properties contain data about the scope, such as the scope range, the lease duration, Domain Name System (DNS) update settings, NAP Configuration, and DHCP/BOOTP configuration options.
Describe IPv4 or IPv6 scope capabilities. However, do not go into depth with IPv6, because the next module covers this.
Explain that you can create scopes by using the New Scope wizard or the netsh command.
References
Microsoft TechNet: Setting Up Scopes:
LAN A
LAN B
Scope A
Scope B
Scope Properties
Network ID
Subnet mask
Scope name
Exclusion range
Lease duration
Network IP address range

13. What Are Superscopes and Multicast Scopes?
Course 6421A
What Are Superscopes and Multicast Scopes?
Module 4: Configuring and Troubleshooting DHCP
DHCP Server
Define superscopes and multicast scopes. Emphasize that these scopes are used for special purposes and are not part of every DHCP deployment.
Provide examples of when you would use superscopes.
What is a superscope?
A superscope is a collection of scopes grouped together into an administrative whole. This allows clients to receive an IP address from multiple logical subnets even when they are on the same physical subnet.
Reasons to use superscopes
One Scope is running out of IP addresses:
A common reason for using a superscope is when a scope has exhausted its address pool. This can occur when the network has grown beyond the original subnet’s maximum amount of hosts. In this case, a superscope can allow the network administrator to add additional addresses for clients to lease from another subnet. It is important to remember that you need to configure the routing infrastructure to recognize the new subnet to support local routing.
You need to renumber an IP Network.
You want to use two DHCP servers on the network for redundancy.
What is a multicast scope?
A collection of multicast addresses (Class D IP addresses) that a multicast group shares. This is an IP address in the Class D range ( ). Applications can request these addresses to send data to multiple hosts without needing to send data to each host individually. These scopes are referred to as Multicast Address Client Allocation Protocol (MADCAP) scopes. Applications that request these addresses must support the MADCAP application programming interface (API).
References
Microsoft TechNet: Setting Up Scopes:
LAN A
LAN B
Scope A and Scope B
DHCP Server
LAN A
LAN B
Scope A
Scope B

14. Demonstration: Configuring DHCP Scopes
Course 6421A
Demonstration: Configuring DHCP Scopes
Module 4: Configuring and Troubleshooting DHCP
In this demonstration, you will see how to:
Create and authorize a DHCP scope
Configure a DHCP superscope
Demonstrate how to configure DHCP scopes to allocate IP addresses to network clients by:
Creating and authorizing a DHCP scope.
Configuring a DHCP superscope.
Demonstration steps:
In the DHCP Microsoft Management Consoles (MMC) console, create and authorize a DHCP scope. Use a private IPv4 network address. (Class C example: Mask: )
Add a second scope in a neighboring subnet: Mask:
Use the Superscope wizard to create a superscope with the two ranges.

15. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
What Are DHCP Options?
Module 4: Configuring and Troubleshooting DHCP
DHCP options are values for common configuration data that applies to the server, scopes, reservations, and class options
Explain the purpose of DHCP options.
DHCP options allow you to apply common settings to computers that you define in scopes.
References
Request for Comments 2132:
Microsoft TechNet: DHCP Resources:
Common scope options are:
DNS Servers
DNS Name
Default Gateway
WINS Servers
WINS Servers

16. What Are DHCP Class-Level Options?
Course 6421A
What Are DHCP Class-Level Options?
Module 4: Configuring and Troubleshooting DHCP
DHCP class-level options are scope options that apply to a specific type of device
Explain that you specify class-level options when you require that a device that belongs to a particular class be configured in a specific way. A class is a logically defined group based on attributes of an IP-based device.
Vendor-class
Ensure that students understand that vendors specify vendor classes internally You cannot change the vendor class. Microsoft’s DHCP server role offers special options based on the vendor class. An example is disabling NetBIOS over TCP/IP for clients with a vendor class matching Windows 2000 or Windows XP.
User-class
You can specify user class as needed when you want to set options for a certain class of users (for example, users from a particular physical location).
References
Microsoft TechNet: DHCP Resources:
Microsoft TechNet: Using option classes:
DHCP class-level option
Description
Vendor-class
Configured by vendors such as Microsoft, HP, and Sun
User-class
Set and viewed by the user

17. What Is a DHCP Reservation?
Course 6421A
What Is a DHCP Reservation?
Module 4: Configuring and Troubleshooting DHCP
A reservation is a specific IP address, within a scope, that is reserved permanently for lease to a specific DHCP client
Explain what a DHCP reservation is.
A DHCP reservation is when an IP address within a scope is set aside for use with a specific DHCP client.
Explain why to use a DHCP reservation.
If you intend to have servers or printers, it often is desirable to provide them with a fixed address. This ensures that IP addresses in a predefined scope will not be assigned inadvertently to another device. This also will ensure that should a scope be depleted of addresses, the devices with reservations will be guaranteed to have an IP address.
Describe the process for configuring a DHCP reservation:
Open the DHCP Server role.
Expand the DHCP scope, and then click Reservations.
Click More Actions, and then click New Reservation.
To configure a reservation, you must know the media access control (MAC) or physical address of the device. This is how the DHCP server knows that the device should have a reservation.
References
Microsoft TechNet: DHCP Resources:
Workstation 1
File and Print Server
Subnet A
Subnet B
DHCP Server
Workstation 2
IP Address1: Leased to Workstation 1
IP Address2: Leased to Workstation 2
IP Address3: Reserved for File and Print Server

18. DHCP Sizing and Availability
Course 6421A
DHCP Clients
DHCP Server1
DHCP Server2
DHCP Sizing and Availability
Module 4: Configuring and Troubleshooting DHCP
Explain the purpose of sizing the environment’s scopes.
For balancing DHCP server usage, a best practice is to use the “80/20” rule to divide the scope addresses between the two DHCP servers. If you configure Server 1 to make available most (approximately 80%) of the addresses, then you can configure Server 2 to make the other addresses (approximately 20%) available to clients.
This also adds a degree of fault tolerance to the DHCP servers by increasing their availability. If one server fails, the second server can continue to renew and provide leases for the clients.
References
Technet: Configuring Scopes:
Technet: DHCP Best Practices:
DHCP Server1 has 20% of addresses as follows:
Scope range:
Excluded addresses:
DHCP Server2 has 80% of addresses as follows:
Excluded addresses: 18

19. How DHCP Options Are Applied
Course 6421A
How DHCP Options Are Applied
Module 4: Configuring and Troubleshooting DHCP
DHCP options can be applied at various levels:
Explain how DHCP applies options to clients’ computers when multiple options are configured at the server, scope, class, and reserved-client level.
DHCP applies options to client computers in a specific order:
Server level
Scope level
Class level
Reserved-client level
It is important that students understand that scope options will override server options. Class options will override both scope and server options. Reserved-client options apply to devices that have a DHCP reservation.
References
Microsoft TechNet: DHCP Resources:
Server
Scope
Class
Reserved client

20. Demonstration: Configuring DHCP Options
Course 6421A
Demonstration: Configuring DHCP Options
Module 4: Configuring and Troubleshooting DHCP
In this demonstration, you will see how to configure DHCP server, scope, and class options
Explain how to configure DHCP options by demonstrating how to:
Configure DHCP server and scope options.
Configure a DHCP user class option.
Configure a DHCP reservation.
Demonstration steps:
Configure DHCP server and scope options:
Using the DHCP MMC console, configure scope options under the scope options node:
(Router, DNS server)
Configure a DHCP user class option:
Using the DHCP MMC console, configure class options. Right-click Server Options, and click the Advanced tab.
Configure a DHCP reservation:
Using the DHCP MMC console, configure a DHCP reservation in the scope that you configured previously.

21. Lesson 3: Managing a DHCP Database
Course 6421A
Lesson 3: Managing a DHCP Database
Module 4: Configuring and Troubleshooting DHCP
Overview of DHCP Management Scenarios
What Is a DHCP Database?
How a DHCP Database Is Backed Up and Restored
How a DHCP Database Is Reconciled
Moving a DHCP Database
DHCP Server Configuration Options
Demonstration: Managing a DHCP Database

22. Overview of DHCP Management Scenarios
Course 6421A
Overview of DHCP Management Scenarios
Module 4: Configuring and Troubleshooting DHCP
The DHCP service needs to be managed to respond to network changes
Scenarios for managing DHCP:
Describe management tasks related to DHCP.
DHCP management scenarios include:
Managing DHCP database growth. The DHCP database is based on a Microsoft Jet database. You need to compact Jet databases on a regular basis.
Backup and restore. Information in the DHCP database is important to maintain. If the DHCP server database becomes corrupt or gets lost, it could lead to significant IP configuration issues.
DHCP database consistency. The database needs to be accurate. If lease data in the DHCP database does not match the lease information on the client, issues such as duplicate IP addresses can occur on the network.
Moving the DHCP database. If the database is very large, it may need to be moved to a larger partition or a better performing volume.
Adding clients.
Adding new network service servers.
Adding new subnets. Adding clients, servers, and subnets can lead to changes in the way the DHCP database is used. These changes require database monitoring and may require new maintenance actions.
Managing DHCP database growth
Protecting the DHCP database
Ensuring DHCP database consistency
Adding clients
Adding new network service servers
Adding new subnets

23. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
What Is a DHCP Database?
Module 4: Configuring and Troubleshooting DHCP
The DHCP database is a dynamic database that contains configuration information
The DHCP database contains DHCP configuration data such as:
Scopes
Address leases
Reservations
Describe the DHCP database
Emphasize that the J50.log file, J50#####.log file, Dhcp.mdb file, and Dhcp.tmp file should not be removed or altered.
Describe compacting the DHCP database.
Ensure that students understand that Jet databases do not recover space automatically when records are erased. Thus, the database is compacted periodically. If the database has an increased amount of usage, it may be necessary to compact the database manually. Starting with Windows NT Server 4.0, dynamic database compaction occurs on DHCP servers as an automatic background process during idle time or after a database update.
References
Microsoft TechNet: DHCP Resources:
Windows Server 2003 stores the DHCP database in the %Systemroot%\System32\Dhcp folder
The DHCP database files include:
Dhcp.mdb
Tmp.edb
J50.log and J50*.log
Res*.log
J50.chk

24. How a DHCP Database Is Backed Up and Restored
Course 6421A
How a DHCP Database Is Backed Up and Restored
Module 4: Configuring and Troubleshooting DHCP
DHCP Server
DHCP
Offline Storage
Restore
Describe how you back up and restore the DHCP database.
Automatic backup (synchronous backup)
Occurs every 60 minutes.
Best practice: Ensure that an offsite backup of the database is kept.
Best practice: Make sure that your automatic backup is to a different volume than that on which your DHCP server is running.
Manual backup (asynchronous backup)
Requires administrative-level permissions. Can also be a member of the DHCP administrators group.
What is backed up:
All scopes, including superscopes and multicast scopes.
Reservations.
Leases.
All options, including server options, scope options, reservation options, and class options.
All registry keys and other configuration settings (for example, audit log settings and folder location settings) set in DHCP server properties. These settings are stored in the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCPServer\Parameters
 To back up this subkey, open Registry Editor, and save the specified key to a text file
Backup Security:
Best Practice: Backups stored on another volume should grant permissions only to the administrative and DHCP administrator groups.
Restore process
References
Microsoft TechNet: Backing up the DHCP database:
Back up
Restore
Back up
The DHCP service automatically backs up the DHCP database to the backup directory on the local drive
If the original database is unable to load, the DHCP service automatically restores from the backup directory on the local drive
In the event that the server hardware fails, the administrator can restore only from the offline storage location
The administrator moves a copy of the backed up DHCP database to an offline storage location

25. How a DHCP Database Is Reconciled
Course 6421A
How a DHCP Database Is Reconciled
Module 4: Configuring and Troubleshooting DHCP
DHCP
Database
Detailed IP address lease information
Compares and reconciles inconsistencies in the DHCP Database
Explain how you reconcile a DHCP database.
Reconciling scopes can fix inconsistencies, such as incorrect or missing information for client IP addresses that are stored in scope-lease information. The DHCP Server service stores the Scope IP address-lease information:
Detailed IP address-lease information, stored in the DHCP database.
Summary IP address-lease information, stored in the DHCP database.
When reconciling scopes, the detail and summary entries are compared to find inconsistencies.
To correct and repair these inconsistencies, you need to reconcile any scope inconsistencies found when performing this operation. Once you select and reconcile scope inconsistencies, the DHCP service either restores those IP addresses to the original owner or creates a temporary reservation for them. These reservations are valid for the lease time assigned to the scope. When the lease time expires, the addresses are recovered for future use.
Registry
Summary IP address lease information
DHCP Server
Example
Registry
DHCP Database
After Reconciliation
Client has IP address
IP address
is available
Lease entry is created in DHCP Database

26. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
Moving a DHCP Database
Module 4: Configuring and Troubleshooting DHCP
DHCP
Database
You can move a DHCP database from one server to another by using the normal backup and restore procedure.
Steps for moving a DHCP database:
Back up database on old server.
Stop the old DHCP server.
Copy database to the new server and, if necessary, install the DHCP server role.
Restore the database.
Start the DHCP server role.
Backup
Media
DHCP
Database
Old DHCP Server
New DHCP Server

27. DHCP Server Configuration Options
Course 6421A
DHCP Server Configuration Options
Module 4: Configuring and Troubleshooting DHCP
Describe DHCP server configuration options.
DHCP server configuration options are the global settings that you define at the server level.
General options
Allow the administrator to set DHCP statistic for debugging and troubleshooting.
DNS options
This is an important panel to configure if there are devices or operating systems that do not update their DNS information automatically. You can configure the DHCP server to update the DNS server if the client is unable to do so.
Network Access Protection options
This panel enables you to enforce NAP for one or more scopes. NAP allows administrators to validate that machines requesting an IP address have been patched to their operating system’s latest version, and that they are running an updated anti-virus program.
Advanced options
Allows the administrator to force the DHCP server to check for IP conflicts when a DHCP client requests a particular IP address. Older clients that do not perform their own check benefit from this. However, this also can cause some overhead. The recommended configuration is to turn this setting off.
The IP binding allows the administrator to specify on which IP address the DHCP server should listen for requests. 27

28. Demonstration: Managing a DHCP Database
Course 6421A
Demonstration: Managing a DHCP Database
Module 4: Configuring and Troubleshooting DHCP
In this demonstration, you will see how to manage a DHCP database
Use the DNS MMC to demonstrate the follow operations:
Back up a DHCP database.
Restore a DHCP database.
Reconcile the DHCP database.

29. Lesson 4: Monitoring and Troubleshooting DHCP
Course 6421A
Lesson 4: Monitoring and Troubleshooting DHCP
Module 4: Configuring and Troubleshooting DHCP
Overview of Monitoring DHCP
Common DHCP Issues
What Are DHCP Statistics?
What Is a DHCP Audit Log File?
Monitoring DHCP Server Performance
Demonstration: Monitoring DHCP

30. Overview of Monitoring DHCP
Course 6421A
Overview of Monitoring DHCP
Module 4: Configuring and Troubleshooting DHCP
Why monitor DHCP?
To observe the dynamic DHCP environment
To determine DHCP server performance
To facilitate planning for current and future needs
Describe methods of, and the reasons for, monitoring DHCP:
To ensure the DHCP service is performing at an acceptable level.
To ensure the DHCP service has sufficient IP addresses to provide to all clients.
To anticipate future growth and proactively address possible issues.
Monitoring tasks include:
DHCP statistics
DHCP events
DHCP performance data
DHCP data includes:
DHCP statistics
DHCP events
DHCP performance data

31. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
Common DHCP Issues
Module 4: Configuring and Troubleshooting DHCP
Address conflicts
Discuss common issues that can occur when you do not configure DHCP properly.
Failure to obtain a DHCP address
Address obtained from incorrect scope
DHCP database suffered data corruption or loss
DHCP server has exhausted its IP address pool

32. What Are DHCP Statistics?
Course 6421A
What Are DHCP Statistics?
Module 4: Configuring and Troubleshooting DHCP
DHCP statistics are collected at either the server level or scope level
Explain that DHCP statistics provide a general view of DHCP activity and usage.
You can configure the refresh rate for the statistics in the server properties General tab.
How to monitor DHCP statistics
Show students the statistics panel in the DHCP Server.
DHCP server statistics
Provide an overview of DHCP server usage. You can use this data to understand the DHCP server’s state quickly.
DHCP scope statistics
Provides basic data about the leases in the DHCP scope.
DHCP Server

33. What Is a DHCP Audit Log File?
Course 6421A
What Is a DHCP Audit Log File?
Module 4: Configuring and Troubleshooting DHCP
A DHCP audit log is a log of service-related events
Describe the purpose of the DHCP audit log.
The audit log provides a traceable log of DHCP server activity that you can use to track lease requests, and grants and denials, and to troubleshoot DHCP server issues.
The audit file is stored in systemroot\system32\dhcp.
The name of the audit file is based on the weekday it was created. For example, if the day of the week is Monday, then the file name is DhcpSrvLog-Mon.log.
Fields that make up a DHCP audit log:
Field Description
ID A DHCP server event ID code
Date The date on which this entry was logged on the DHCP server
Time The time at which this entry was logged on the DHCP server
Description A description of this DHCP server event
IP Address The IP address of the DHCP client
Host Name The host name of the DHCP client
MAC Address The MAC address that the network adapter hardware of the client uses
Common Event ID codes
ID,Date,Time,Description,IP Address,Host Name,MAC Address
00,06/08/03,22:35:10,Started,,,,
56,06/08/03,22:35:10,Authorization failure, stopped servicing,,domain1.local,,
55,06/08/03,22:45:38,Authorized(servicing),,domain1.local
References
Microsoft TechNet: Audit logging:

34. Monitoring DHCP Server Performance
Course 6421A
Monitoring DHCP Server Performance
Module 4: Configuring and Troubleshooting DHCP
Performance counters
What to look for after a baseline is established
Packets received/second
Monitor for sudden increases or decreases, which could reflect network problems
Requests/second
Active queue length
Monitor for both sudden and gradual increases, which could reflect increased load or decreased server capacity
Duplicates dropped/second
Monitor for any activity that could indicate that more than one request is being transmitted on behalf of clients
Create a DHCP performance baseline
Explain how to monitor DHCP server performance.
The DHCP performance counters become available after you install the DHCP Server role. Once available, you can load the performance counters using the performance monitor.
Describe the guidelines for monitoring the performance of a DHCP server.
A DHCP server typically should not come under a heavy network load. However, if you notice the queue lengths are logging consistently high values, you should check the server for bottlenecks that could be slowing DHCP performance.
Common performance counters include:
Packets received/second
Packets expired/second
Requests/second
Milliseconds per packet
Active queue length
Duplicates dropped/second
References
Microsoft TechNet: DHCP performance monitoring reference:
Check the standard counters for server performance
Review DHCP server counters for significant changes in DHCP traffic

35. Demonstration: Monitoring DHCP
Course 6421A
Demonstration: Monitoring DHCP
Module 4: Configuring and Troubleshooting DHCP
In this demonstration, you will see how to monitor DHCP statistics and performance
Explain how to monitor DHCP statistics and performance by demonstrating how to:
View DHCP statistics.
Configure DHCP audit logging.
Configure DHCP performance counters.

36. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
Lesson 5: Securing DHCP
Module 4: Configuring and Troubleshooting DHCP
Securing DHCP
Preventing an Unauthorized User from Obtaining a Lease
Restricting Unauthorized, Non-Microsoft DHCP Servers from Leasing IP Addresses
Restricting DHCP Administration

37. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
Securing DHCP
Module 4: Configuring and Troubleshooting DHCP
Reasons for securing DHCP include:
Preventing an unauthorized user from obtaining a lease
List the reasons for securing DHCP:
Preventing an unauthorized user from obtaining a lease
Restricting unauthorized, non-Microsoft DHCP servers from leasing IP addresses
Restricting DHCP administration
Note: This topic is for overview purposes only. Each of the reasons for securing DHCP is discussed in more detail in this lesson’s remaining topics.
Restricting unauthorized, non-Microsoft DHCP servers from leasing IP addresses
Restricting DHCP administration

38. Preventing an Unauthorized User from Obtaining a Lease
Course 6421A
Preventing an Unauthorized User from Obtaining a Lease
Module 4: Configuring and Troubleshooting DHCP
To prevent an unauthorized user from obtaining a lease:
Ensure that unauthorized persons do not have physical or wireless access to your network
Discuss the guidelines for preventing an unauthorized user from obtaining a lease.
Emphasize that the only way to completely prevent unauthorized access using only DHCP is to disallow network access. However, this is not feasible. The next best action is to limit the possibility of somebody plugging into an empty network jack or to implement security on a wireless network.
Use NAP to validate a client computer’s health. NAP can determine if the computer is running an up-to-date antivirus program and the latest Windows updates. If the computer is not compliant with the NAP policy, it can be denied network access or it can be relegated to a remediation network where it may obtain the necessary updates to become compliant.
You also can use NAP to restrict access to a network based on whether the user is authorized for network access.
Enable audit logging for every DHCP server on your network
Regularly check and monitor audit log files
Use 802.1X-enabled LAN switches or wireless access points to access the network
Configure NAP to validate users and security policy compliance

39. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
Restricting Unauthorized, Non-Microsoft DHCP Servers from Leasing IP Addresses
Module 4: Configuring and Troubleshooting DHCP
DHCP authorization
Available on Windows 2000 and Windows Server 2003
Mention to students that users must disable DHCP services from other devices, such as routers or third-party tools.
If users complain of network access problems, check the IP settings that the DHCP server is providing by using the following command:
ipconfig.exe/all
If the DHCP server result is not correct, investigating the IP address in question should identify the problem.
The only way to restrict these servers is to find their source IP and to remove them from the network.
Dhcploc.exe is a utility that you can use to locate rogue DHCP servers on a network.
Authorization not required on other DHCP implementations
To restrict an unauthorized, non-Microsoft DHCP server from leasing IP addresses, ensure that unauthorized persons do not have physical or wireless access to your network

40. Restricting DHCP Administration
Course 6421A
Restricting DHCP Administration
Module 4: Configuring and Troubleshooting DHCP
To restrict who can administer the DHCP service:
Limit the members of the DHCP Administrators group
Restrict who can administer the DHCP server role
The DHCP Administrators group is located in the built-in groups on domain controllers or on local servers because the DHCP Administrators local group is used to restrict and grant access to administer DHCP servers.
Permissions required to authorize and administer DHCP
Authorization of a DHCP service is available only to Enterprise administrators. If the need exists for a down-level administrator to authorize the domain, it can be done using Active Directory® directory service delegation.
DHCP Administrators
Any user in the DHCP Administrators group can manage the DHCP service on the server.
DHCP Users
Any user in the DHCP Users group can have read-only access to the console.
Add users needing read-only access to the DHCP Users group
Account
Permissions
DHCP Administrators group
Can view and modify any data about the DHCP server
DHCP Users group
Has read-only DHCP console access to the server

41. Lab: Configuring and Troubleshooting the DHCP Server Role
Course 6421A
Lab: Configuring and Troubleshooting the DHCP Server Role
Module 4: Configuring and Troubleshooting DHCP
Exercise 1: Installing and Authorizing the DHCP Server Role
Exercise 2: Configuring a DHCP Scope
Exercise 3: Troubleshooting Common DHCP Issues
Lab objectives:
Install and authorize the DHCP server role
Configure a DHCP Scope and scope options
Troubleshoot common DHCP issues
Scenario:
You need to implement a new Windows Server 2008 DHCP server role within the Woodgrove Bank networking environment.
Exercise 1: Installing and Authorizing the DHCP Server Role
The students will install the DHCP server role and ensure that it is authorized in Active Directory.
Exercise 2: Configuring a DHCP Scope
Students will perform the following tasks:
Configure DHCP scope and scope options.
Validate that DHCP works as expected.
Exercise 3: Troubleshooting Common DHCP Issues
Students will run a script that will configure the DHCP server so that it will not work properly. Using the available information, they will then fix the configuration problems that the script caused.
Inputs:
Provided scenario
Virtual machines
Output:
DHCP server role installed and configured.
Logon information
Virtual machine
NYC-DC1, NYC-CL1
User name
Administrator
Password
Pa$$w0rd
Estimated time: 30 minutes

42. Module 4: Configuring and Troubleshooting DHCP
Course 6421A
Lab Review
Module 4: Configuring and Troubleshooting DHCP
What kind of account is necessary to authorize a DHCP server?
Why is it important to define an exclusion range when configuring the DHCP scope?
What is the consequence of not providing a default gateway when configuring DHCP scope options?
Question: What kind of account is necessary to authorize a DHCP server?
Answer: An Enterprise administrative account is necessary to authorize a DHCP server in a domain.
Question: Why is it important to define an exclusion range when configuring the DHCP scope?
Answer: So that DHCP does not lease the IP addresses of devices that are assigned static IP addresses in the exclusion range, which could cause a possible IP conflict.
Question: What is the consequence of not providing a default gateway when configuring DHCP scope options?
Answer: The computers that you configure with that scope may not be able to communicate outside their own network. If you require Internet connectivity, then you must configure computers with a default gateway.

43. Module Review and Takeaways
Course 6421A
Module Review and Takeaways
Module 4: Configuring and Troubleshooting DHCP
Review Questions
Common Issues and Troubleshooting Tips
Best Practices
Tools
Review Questions
Question: What is the main benefit of using DHCP?
Answer: The main benefit is automatic configuration of IP addresses for client computers.
Question: With what new security feature does DHCP integrate to force client computers to be compliant with company security policies ?
Answer: Network Access Protection (NAP)
Question: What are the four DHCP message broadcasts that are used when a successful address lease occurs?
Answer:
DHCPDISCOVER
DHCPOFFER
DHCPREQUEST
DHCPACK
Question: At what point in a DHCP lease does the client usually renew the lease automatically?
Answer: When 50 percent of the lease duration has expired.
Question: Why would you use a superscope?
You are running out of IP addresses in a subnet and need additional IPs for an expanding base of users and devices.
You need to transition clients from one IP subnet to another over a period of time, and you want the transition to occur transparently.
Question: What are the three data sources for monitoring DHCP?
DHCP Statistics
DHCP Events
DHCP Event data