1. DHCP
Dynamic Host Configuration Protocol

2. Objectives Describe the DHCP lease and renewal process
Understand and describe the purpose of a DHCP relay
Install DHCP
Configure DHCP scopes, superscopes, reservations, vendor classes, and user classes
Manage and monitor DHCP
Troubleshoot DHCP
Install and configure a DHCP relay

3. The DHCP Process
Used to automatically deliver IP addressing information to client computers on a network
Can also deliver IP address information to servers and other devices such as printers
Use of DHCP reduces time spent configuring computers on network
Client computers use DHCP by default unless static IP address is specified during installation

4. Windows XP TCP/IP Properties

5. Leasing an IP Address
Process to lease an address is composed of four packets
DHCPDISCOVER: sent from the client computer to the broadcast IP address
DHCPOFFER: response sent after receiving DHCPDISCOVER packet
DHCPREQUEST: response of DHCP client after receiving DHCPOFFER packet
DHCPACK: response sent by chosen DHCP server indicating confirmation that lease has been chosen and client can now use the lease

6. The Four Packets in the DHCP Lease Process

7. Renewing an IP Address
An IP address leased using DHCP can be either permanent or timed
Permanent address
DHCP server never reuses the address for another client
Timed lease
Allows clients to use an IP address for a specified period of time
Windows clients attempt to renew their lease after 50% of lease time has expired
ipconfig /release command is used to force the release of a DHCP address

8. The DHCP Lease Renewal Process

9. DHCP Relay DHCP packets DHCP relay
Are broadcast packets during the leasing process
Cannot travel across a router
DHCP relay
Receives broadcast DHCP packets from clients and forwards them as unicast packets to a DHCP server
Must be configured with IP address of the DHCP server to deliver unicast packets
DHCP Relay Service cannot be installed on the same server as the DHCP Service

10. Installing DHCP

11. Authorization Control over DHCP is very important
An unauthorized DHCP server can quickly hand out incorrect IP addressing information to hundreds of client computers
To exercise control over DHCP
Windows Server 2003 must be authorized to start DHCP Service
Authorization of a DHCP server takes place in Active Directory

12. Authorization (Continued)
To authorize DHCP server
Must be a member of Enterprise Admins group or
Member of Enterprise Admins group must delegate permissions to you

13. Unauthorized DHCP server error in Event Viewer

14. The DHCP Management Snap-In

15. Authorized DHCP server information in Event Viewer

16. Configuring DHCP
Normally accomplished with the DHCP management snap-in
NETSH
Command used to configure DHCP
Used in larger organizations where there is a need to make changes programmatically using batch files

17. Configuring DHCP (Continued)
DHCP elements that can be configured include
Scopes
Superscopes
Multicast scopes
Reservations
Vendor and user classes
Scope, server, and reservation options

18. Scopes
Used to define a range of IP addresses for the DHCP server to hand out to client computers
Each scope is configured with
Name
Description
Starting IP address
Ending IP address
Subnet mask
Exclusions
Lease duration

19. Scopes (Continued) Name and description
Appears in the DHCP management snap-in
Starting and ending IP addresses
Define range of IP addresses that can be handed out by the DHCP server
Strategies when defining starting and ending IP addresses
Configure scope to use all available addresses on a subnet, then exclude the static IP addresses being used by hosts
Configure scope to use addresses that are not already in use

20. Scopes (Continued) Exclusions Lease duration DHCP server
Used to prevent some IP addresses in a scope from being handed out dynamically
Lease duration
Defines how long client computers are allowed to use an IP address
Default lease duration used by Windows Server 2003 is eight days
DHCP server
Does not begin using a scope immediately after creation
Scope must be activated before DHCP Service can begin using the scope

21. Scope Settings

22. Superscopes
Used to combine multiple scopes into a single logical scope
Used when a single physical part of the network has two subnets

23. A Superscope Containing Two Scopes

24. Multicast Scopes
Used to deliver multicast addresses to applications that require it
Time To Live (TTL)
Defines the number of routers through which a multicast packet can move
Exclusions
Define addresses between the start and end IP addresses that are not handed out
Lease duration
The length of time that an application can use a multicast address
Default lease length is 30 days

25. Reservations
Used to hand out a specific IP address to a particular client computer or device on the network
Can also be beneficial when firewalls are in place
Created based on the MAC address of the network card

26. Creating a Reservation

27. Configuring Options
DHCP can hand out the following IP configuration options
Default gateway
DNS server
WINS server
DNS is often configured at the server level

28. Summary DHCP DHCP lease process Dynamically assigns IP addresses
Can assign multicast IP addresses
DHCP lease process
Composed of DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, and DHCPACK
DHCPNAK: used by DHCP servers to decline renewal of lease
DHCPRELEASE: used by clients to inform DHCP server that lease is no longer required

29. Summary (Continued) Renewing lease
Clients attempt to renew at 50%, 87.5%, and 100% of lease time
Commands ipconfig /release and ipconfig /renew
Can release and renew DHCP leases
DHCP server
Must be authorized in Active Directory to lease addresses
Must be member of Enterprise Admins to authorize DHCP

30. Summary (Continued) Scope Superscope Exclusion in scope
Defines range of IP addresses that are leased to clients
Must be activated before DHCP server leases addresses in the scope
Superscope
Combines two scopes into single scope
Exclusion in scope
Used to stop a DHCP server from handing out specific addresses or range of addresses within a scope