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  1. 1. 70-291: MCSE Guide to Managing a Microsoft Windows Server 2003 Network Chapter 4: Dynamic Host Configuration Protocol
  2. 2. Objectives <ul><li>Outline the benefits of using DHCP </li></ul><ul><li>Describe the DHCP lease and renewal process </li></ul><ul><li>Install and authorize the DHCP service </li></ul><ul><li>Configure DHCP scopes </li></ul><ul><li>Create DHCP reservations for client computers </li></ul><ul><li>Configure DHCP options </li></ul><ul><li>Understand and describe the purpose of a DHCP relay </li></ul><ul><li>Install and configure a DHCP relay </li></ul>
  3. 3. DHCP Overview <ul><li>Used to automatically deliver IP addressing </li></ul><ul><li>Reduces the amount of time you spend configuring computers on your network </li></ul><ul><li>Used by default unless you specify otherwise </li></ul><ul><li>The ipconfig /all command will indicate whether the configuration came from a DHCP server computer </li></ul>
  4. 4. DHCP Overview (continued)
  5. 5. DHCP Overview (continued)
  6. 6. Leasing an IP Address <ul><li>An IP address is leased during the boot process </li></ul><ul><li>The overall process is composed of four broadcast packets: </li></ul><ul><ul><li>DHCPDISCOVER </li></ul></ul><ul><ul><li>DHCPOFFER </li></ul></ul><ul><ul><li>DHCPREQUEST </li></ul></ul><ul><ul><li>DHCPACK </li></ul></ul>
  7. 7. Leasing an IP Address (continued) <ul><li>Any DHCP server that receives the DHCPDISCOVER packet responds with a DHCPOFFER packet </li></ul><ul><li>The DHCP client responds to the DHCPOFFER packet it receives with a DHCPREQUEST packet </li></ul><ul><li>A DHCPACK packet indicates confirmation that the client can use the lease </li></ul><ul><li>Once DHCPACK is received, the client can start using the IP address and options in the lease </li></ul>
  8. 8. Leasing an IP Address (continued)
  9. 9. Renewing an IP Address <ul><li>The IP address can either be permanent or timed </li></ul><ul><li>A permanent address is never reused for another client </li></ul><ul><li>Timed leases expire after a certain amount of time </li></ul><ul><li>Windows clients attempt to renew their lease after 50% of the lease time has expired </li></ul><ul><li>A DHCP server may either honor or reject a renew request </li></ul>
  10. 10. Renewing an IP Address (continued)
  11. 11. Installing and Authorizing the DHCP Service <ul><li>A DHCP service must be authorized after installation </li></ul>
  12. 12. Installing the DHCP Service <ul><li>DHCP is a standard service </li></ul><ul><li>It is included in Windows Server 2003 </li></ul><ul><li>It is not installed as part of a default installation </li></ul>
  13. 13. Installing the DHCP Service (continued)
  14. 14. Activity 4-1: Installing DHCP <ul><li>Objective: Install DHCP on Windows Server 2003 </li></ul><ul><li>Make sure your network connection is statically configured </li></ul><ul><li>Install the service using the Add/Remove Windows Components utility </li></ul>
  15. 15. Authorizing the DHCP Service <ul><li>Unauthorized DHCP servers can hand out bad information </li></ul><ul><li>DHCP will not start unless authorized </li></ul><ul><li>If Active Directory is used, authorization takes place in Active Directory </li></ul><ul><li>DHCP servers are automatically authorized under certain conditions </li></ul>
  16. 16. Authorizing the DHCP Service (continued)
  17. 17. Authorizing the DHCP Service (continued)
  18. 18. Activity 4-2: Starting an Authorized DHCP Server <ul><li>Objective: View the results of starting a DHCP server that does not participate in an Active Directory domain </li></ul><ul><li>Check to make sure the service is running </li></ul><ul><li>Check out any relevant events using the System Log </li></ul>
  19. 19. Activity 4-3: Installing the Active Directory Service <ul><li>Objective: Install the Active Directory service on your computer and participate in an Active Directory domain </li></ul><ul><li>Use the dcpromo utility </li></ul><ul><li>Select “domain controller for a new domain” </li></ul><ul><li>Select “domain in a new forest” </li></ul><ul><li>Continue through the resulting dialogs </li></ul>
  20. 20. Activity 4-4: Starting an Unauthorized DHCP Server <ul><li>Objective: View the results of starting an unauthorized DHCP server </li></ul><ul><li>View the System Log to see the result of starting an unauthorized DHCP server </li></ul>
  21. 21. Activity 4-5: Authorizing a DHCP Server <ul><li>Objective: Authorize a DHCP server in Active Directory </li></ul><ul><li>Go to the DHCP snap-in and choose the activate option </li></ul>
  22. 22. Configuring DHCP Scopes <ul><li>Scope defines a range of IP addresses </li></ul><ul><li>Each scope is configured with: </li></ul><ul><ul><li>Description </li></ul></ul><ul><ul><li>Starting IP address </li></ul></ul><ul><ul><li>Ending IP address </li></ul></ul><ul><ul><li>Subnet mask </li></ul></ul><ul><ul><li>Exclusions </li></ul></ul><ul><ul><li>Lease duration </li></ul></ul><ul><li>Two strategies exist for defining the starting and ending IP addresses </li></ul><ul><ul><li>Allow all and exempt the few static addresses </li></ul></ul><ul><ul><li>Use only the addresses not already in use </li></ul></ul>
  23. 23. Configuring DHCP Scopes (continued)
  24. 24. Configuring DHCP Scopes (continued) <ul><li>Exclusions are used to prevent some IP addresses from being handed out dynamically </li></ul><ul><li>Lease duration defines how long client computers are allowed to use an IP address </li></ul><ul><li>Default lease duration is eight days </li></ul><ul><li>A scope must be activated before the DHCP service can begin using it </li></ul>
  25. 25. Activity 4-6: Creating a Scope <ul><li>Objective: Create a scope to distribute IP addresses to client computers </li></ul><ul><li>Manually enter the IP configuration settings as directed by the text </li></ul><ul><li>Create a new scope using the configuration settings provided </li></ul>
  26. 26. Activity 4-7: Activating and Testing a Scope <ul><li>Objective: Activate a DHCP scope, and then test it with a partner </li></ul><ul><li>One person will activate the scope created in the previous activity </li></ul><ul><li>Another person will try to obtain an automatic IP address from the server </li></ul>
  27. 27. Superscopes <ul><li>Used to combine multiple scopes into a single logical scope </li></ul><ul><li>Allows multiple scopes to be treated as a single scope </li></ul><ul><li>If a superscope is used, then the DHCP server offers only one lease as opposed to multiple leases </li></ul>
  28. 28. Superscopes (continued)
  29. 29. Activity 4-8: Configuring a Superscope <ul><li>Objective: Combine two scopes into a single logical unit using a superscope </li></ul><ul><li>First, create a second scope in addition to the scope already created in a previous activity </li></ul><ul><li>Create a superscope to encompass the two scopes </li></ul><ul><li>Use the DHCP snap-in for this activity </li></ul>
  30. 30. Activity 4-9: Deleting a Superscope <ul><li>Objective: Delete a superscope, leaving each scope independent </li></ul><ul><li>Make sure you delete the superscope without deleting the subscopes </li></ul>
  31. 31. Multicast Scopes <ul><li>Used to deliver multicast addresses to applications that require it </li></ul><ul><li>Multicast addresses are used to deliver packets to groups of computers </li></ul><ul><li>Start and end IP addresses define the range of addresses that can be handed out by DHCP servers </li></ul><ul><li>TTL defines the number of routers through which a multicast packet can move </li></ul>
  32. 32. Multicast Scopes (continued) <ul><li>Exclusions define addresses that should not be handed out </li></ul><ul><li>Lease duration defines the length of time that an application can use a multicast address </li></ul><ul><li>Default lease length is 30 days </li></ul>
  33. 33. Activity 4-10: Creating a Multicast Scope <ul><li>Objective: Create a multicast scope to deliver multicast addresses to applications </li></ul><ul><li>Setting up a multicast scope is very similar to setting up any other scope </li></ul><ul><li>Set the scope configuration to that specified in the text </li></ul>
  34. 34. Activity 4-11: Deleting a Multicast Scope <ul><li>Objective: Delete a multicast scope </li></ul><ul><li>Right click on the scope and issue the delete command </li></ul>
  35. 35. Creating DHCP Reservations <ul><li>Reservations are used to hand out a specific IP address to a particular client </li></ul><ul><li>Useful when delivering IP addresses to devices that would normally use static addresses </li></ul><ul><li>Can also be beneficial when firewalls are in place </li></ul><ul><li>Reservations are created based on MAC addresses </li></ul>
  36. 36. Creating DHCP Reservations (continued)
  37. 37. Activity 4-12: Creating and Testing a Reservation <ul><li>Objective: Create a DHCP reservation, and test it with a client </li></ul><ul><li>Configure the server to reserve an IP address for a client machine </li></ul><ul><li>Test to see if the client machine picks up the reserved address </li></ul>
  38. 38. Configuring DHCP Options <ul><li>DHCP can hand out a variety of other IP configuration options </li></ul><ul><li>It is common that all workstations within an entire organization use the same DNS servers </li></ul><ul><li>DNS is often configured at the server level </li></ul>
  39. 39. Configuring DHCP Options (continued)
  40. 40. Configuring DHCP Options (continued)
  41. 41. Activity 4-13: Setting Server Options <ul><li>Objective: Set the DNS server option for a DHCP server </li></ul><ul><li>Check 006 DNS servers option </li></ul><ul><li>Add the IP address x.0.0.250 </li></ul>
  42. 42. Activity 4-14: Setting Scope Options <ul><li>Objective: Set the default gateway in the scope options </li></ul><ul><li>Use the DHCP snap-in to complete this activity </li></ul>
  43. 43. Activity 4-15: Testing Server & Scope Options <ul><li>Objective: Activate a DHCP scope, and then test it with a partner to ensure that scope options are handed out </li></ul><ul><li>Activate a DHCP scope </li></ul><ul><li>Configure a client to access the server </li></ul><ul><li>Check the default gateway and DNS settings to find out whether or not the configurations entered in previous activities were done correctly </li></ul>
  44. 44. Vendor and User Classes <ul><li>Used to differentiate between clients within a scope </li></ul><ul><li>Vendor classes are based on the operating system </li></ul><ul><li>User classes are defined based on network connectivity or the administrator </li></ul><ul><li>You can use the ipconfig /setclassid command to set the DHCP user class ID </li></ul>
  45. 45. Vendor and User Classes (continued)
  46. 46. Vendor and User Classes (continued)
  47. 47. Configuring a DHCP Relay <ul><li>DHCP packets cannot travel across a router </li></ul><ul><li>A relay agent is necessary in order to have a single DHCP server handle all leases </li></ul><ul><li>Relay agents receive broadcast DHCP packets and forward them as unicast packets to a DHCP server </li></ul><ul><li>The DHCP relay cannot be installed on the same server as the DHCP service </li></ul>
  48. 48. Configuring a DHCP Relay (continued)
  49. 49. Configuring a DHCP Relay (continued)
  50. 50. Activity 4-16: Configuring a DHCP Relay <ul><li>Objective: Uninstall the DHCP service from your computer and configure it as a DHCP relay </li></ul><ul><li>Uninstall the DHCP service </li></ul><ul><li>Configure the computer as a relay by using the Routing and Remote Access tool provided in Windows </li></ul>
  51. 51. Summary <ul><li>DHCP dynamically assigns IP address information to clients on a network </li></ul><ul><li>The DHCP lease process is composed of four packets: </li></ul><ul><ul><li>DHCPDISCOVER </li></ul></ul><ul><ul><li>DHCPOFFER </li></ul></ul><ul><ul><li>DHCPREQUEST </li></ul></ul><ul><ul><li>DHCPACK </li></ul></ul><ul><li>A DHCP client attempts to renew its lease at 50%, 87.5%, and 100% of the lease time </li></ul><ul><li>The commands ipconfig /release and ipconfig /renew can be used to release and renew DHCP leases </li></ul>
  52. 52. Summary (continued) <ul><li>If the Active Directory service is present on your network, each DHCP server must be authorized in Active Directory to lease addresses to clients </li></ul><ul><li>A scope defines a range of IP addresses that are leased to clients </li></ul><ul><li>A superscope combines two scopes into a single logical unit to service network segments with two subnets </li></ul>
  53. 53. Summary (continued) <ul><li>An exclusion in a scope can stop a DHCP server from handing out specific addresses </li></ul><ul><li>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 </li></ul><ul><li>Vendor and user classes can be used to configure some client computers with different options, depending on the class to which they belong </li></ul><ul><li>A DHCP relay agent is required on each network that requires IP configuration from a DHCP server across a router </li></ul>