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  1. 1. Dynamic Host Configuration Protocol
  2. 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. 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
  4. 4. 4 DHCP Overview (continued)
  5. 5. 5 DHCP Overview (continued)
  6. 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. 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
  8. 8. 8 Leasing an IP Address (continued)
  9. 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
  10. 10. 10 Renewing an IP Address (continued)
  11. 11. 11 Installing and Authorizing the DHCP Service • A DHCP service must be authorized after installation
  12. 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
  13. 13. 13 Installing the DHCP Service (continued)
  14. 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. 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
  16. 16. 16 Authorizing the DHCP Service (continued)
  17. 17. 17 Authorizing the DHCP Service (continued)
  18. 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. 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. 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. 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. 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
  23. 23. 23 Configuring DHCP Scopes (continued)
  24. 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. 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. 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. 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
  28. 28. 28 Creating DHCP Reservations (continued)
  29. 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. 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
  31. 31. 31 Configuring DHCP Options (continued)
  32. 32. 32 Configuring DHCP Options (continued)
  33. 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. 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. 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. 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
  37. 37. 37 Configuring a DHCP Relay (continued)
  38. 38. 38 Configuring a DHCP Relay (continued)
  39. 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. 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. 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. 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