2. 2
Objectives
• Outline the benefits of using DHCP
• Describe the DHCP lease and renewal process
• Install and authorize the DHCP service
• Configure DHCP scopes
• Create DHCP reservations for client computers
• Configure DHCP options
• Understand and describe the purpose of a DHCP
relay
• Install and configure a DHCP relay
3. 3
DHCP Overview
• Used to automatically deliver IP addressing
• Reduces the amount of time you spend configuring
computers on your network
• Used by default unless you specify otherwise
• The ipconfig /all command will indicate whether the
configuration came from a DHCP server computer
6. 6
Leasing an IP Address
• An IP address is leased during the boot process
• The overall process is composed of four broadcast
packets:
• DHCPDISCOVER
• DHCPOFFER
• DHCPREQUEST
• DHCPACK
7. 7
Leasing an IP Address
(continued)
• Any DHCP server that receives the DHCPDISCOVER
packet responds with a DHCPOFFER packet
• The DHCP client responds to the DHCPOFFER
packet it receives with a DHCPREQUEST packet
• A DHCPACK packet indicates confirmation that the
client can use the lease
• Once DHCPACK is received, the client can start using
the IP address and options in the lease
9. 9
Renewing an IP Address
• The IP address can either be permanent or timed
• A permanent address is never reused for another
client
• Timed leases expire after a certain amount of time
• Windows clients attempt to renew their lease after
50% of the lease time has expired
• A DHCP server may either honor or reject a renew
request
12. 12
Installing the DHCP Service
• DHCP is a standard service
• It is included in Windows Server 2003
• It is not installed as part of a default installation
14. 14
Activity 4-1: Installing DHCP
• Objective: Install DHCP on Windows Server 2003
• Make sure your network connection is statically
configured
• Install the service using the Add/Remove Windows
Components utility
15. 15
Authorizing the DHCP Service
• Unauthorized DHCP servers can hand out bad
information
• DHCP will not start unless authorized
• If Active Directory is used, authorization takes place
in Active Directory
• DHCP servers are automatically authorized under
certain conditions
18. 18
Activity 4-2:
Starting an Authorized DHCP
Server
• Objective: View the results of starting a DHCP server
that does not participate in an Active Directory
domain
• Check to make sure the service is running
• Check out any relevant events using the System Log
19. 19
Activity 4-3:
Installing the Active Directory
Service
• Objective: Install the Active Directory service on
your computer and participate in an Active Directory
domain
• Use the dcpromo utility
• Select “domain controller for a new domain”
• Select “domain in a new forest”
• Continue through the resulting dialogs
20. 20
Activity 4-4:
Starting an Unauthorized DHCP
Server
• Objective: View the results of starting an unauthorized
DHCP server
• View the System Log to see the result of starting an
unauthorized DHCP server
21. 21
Activity 4-5:
Authorizing a DHCP Server
• Objective: Authorize a DHCP server in Active
Directory
• Go to the DHCP snap-in and choose the activate
option
22. 22
Configuring DHCP Scopes
• Scope defines a range of IP addresses
• Each scope is configured with:
• Description
• Starting IP address
• Ending IP address
• Subnet mask
• Exclusions
• Lease duration
• Two strategies exist for defining the starting and
ending IP addresses
• Allow all and exempt the few static addresses
• Use only the addresses not already in use
24. 24
Configuring DHCP Scopes
(continued)
• Exclusions are used to prevent some IP addresses
from being handed out dynamically
• Lease duration defines how long client computers are
allowed to use an IP address
• Default lease duration is eight days
• A scope must be activated before the DHCP service
can begin using it
25. 25
Activity 4-6: Creating a Scope
• Objective: Create a scope to distribute IP addresses to
client computers
• Manually enter the IP configuration settings as
directed by the text
• Create a new scope using the configuration settings
provided
26. 26
Activity 4-7:
Activating and Testing a Scope
• Objective: Activate a DHCP scope, and then test it
with a partner
• One person will activate the scope created in the
previous activity
• Another person will try to obtain an automatic IP
address from the server
27. 27
Creating DHCP Reservations
• Reservations are used to hand out a specific IP
address to a particular client
• Useful when delivering IP addresses to devices that
would normally use static addresses
• Can also be beneficial when firewalls are in place
• Reservations are created based on MAC addresses
29. 29
Activity 4-12:
Creating and Testing a
Reservation
• Objective: Create a DHCP reservation, and test it
with a client
• Configure the server to reserve an IP address for a
client machine
• Test to see if the client machine picks up the reserved
address
30. 30
Configuring DHCP Options
• DHCP can hand out a variety of other IP configuration
options
• It is common that all workstations within an entire
organization use the same DNS servers
• DNS is often configured at the server level
33. 33
Activity 4-13:
Setting Server Options
• Objective: Set the DNS server option for a DHCP
server
• Check 006 DNS servers option
• Add the IP address x.0.0.250
34. 34
Activity 4-14:
Setting Scope Options
• Objective: Set the default gateway in the scope
options
• Use the DHCP snap-in to complete this activity
35. 35
Activity 4-15:
Testing Server & Scope Options
• Objective: Activate a DHCP scope, and then test it
with a partner to ensure that scope options are handed
out
• Activate a DHCP scope
• Configure a client to access the server
• Check the default gateway and DNS settings to find
out whether or not the configurations entered in
previous activities were done correctly
36. 36
Configuring a DHCP Relay
• DHCP packets cannot travel across a router
• A relay agent is necessary in order to have a single
DHCP server handle all leases
• Relay agents receive broadcast DHCP packets and
forward them as unicast packets to a DHCP server
• The DHCP relay cannot be installed on the same
server as the DHCP service
39. 39
Activity 4-16:
Configuring a DHCP Relay
• Objective: Uninstall the DHCP service from your
computer and configure it as a DHCP relay
• Uninstall the DHCP service
• Configure the computer as a relay by using the
Routing and Remote Access tool provided in
Windows
40. 40
Summary
• DHCP dynamically assigns IP address information to clients
on a network
• The DHCP lease process is composed of four packets:
• DHCPDISCOVER
• DHCPOFFER
• DHCPREQUEST
• DHCPACK
• A DHCP client attempts to renew its lease at 50%, 87.5%, and
100% of the lease time
• The commands ipconfig /release and ipconfig /renew can be
used to release and renew DHCP leases
41. 41
Summary (continued)
• If the Active Directory service is present on your
network, each DHCP server must be authorized in
Active Directory to lease addresses to clients
• A scope defines a range of IP addresses that are
leased to clients
• A superscope combines two scopes into a single
logical unit to service network segments with two
subnets
42. 42
Summary (continued)
• An exclusion in a scope can stop a DHCP server from
handing out specific addresses
• A reservation allows you to give a specific
workstation a defined IP address by tying the DHCP
lease to the MAC address of the client
• Vendor and user classes can be used to configure
some client computers with different options,
depending on the class to which they belong
• A DHCP relay agent is required on each network that
requires IP configuration from a DHCP server across
a router
