DHCP PROTOCOL
- 1. • Lesson 3 Setting up DHCP Server Mangesh
- 2. Dynamic Host Configuration Protocol (DHCP) • Each host must have an Internet Protocol (IP) address and a subnet mask, and if communicating outside the local subnet, each must also have a default gateway. • Each IP address must be valid and unique within the host’s internetwork. • Manually managing IP addresses is a complex tedious task. • The Dynamic Host Configuration Protocol (DHCP) simplifies this process by automating the assigning, tracking, and reassigning of IP addresses.
- 3. Dynamic Host Configuration Protocol (DHCP) • DHCP is based heavily on BOOTP. • DHCP can dynamically allocate an IP address from a pool of addresses and then reclaim it when it is no longer needed. • Because this process is dynamic, no duplicate addresses are assigned by a properly configured DHCP server, and administrators can move computers between subnets without manually configuring them.
- 4. Dynamic Host Configuration Protocol (DHCP) • Each Microsoft Windows Server 2008 edition (the Standard Edition, Enterprise Edition, and Datacenter Edition) include the DHCP Server service. • DHCP is an optional installation. • All Microsoft Windows clients automatically install the DHCP Client service as part of TCP/IP, including Windows Server 2008, Windows Server 2008, Microsoft Windows Vista, and Microsoft Windows XP.
- 5. Dynamic Host Configuration Protocol (DHCP) • Four Key benefits to DHCP: – Centralized administration of IP configuration. – Dynamic host configuration. – Seamless IP host configuration. – Flexibility and scalability.
- 6. DHCP Terminology • DHCP client - A computer that obtains its configuration information from DHCP. • DHCP server - A computer that provides DHCP configuration information to multiple clients. – The IP addresses and configuration information that the DHCP server makes available to the client are defined by the DHCP administrator. Shantanu
- 7. DHCP Terminology • DHCP lease - This defines the duration for which a DHCP server assigns an IP address to a DHCP client. – The lease duration can be any amount of time between 1 minute and 999 days, or it can be unlimited. – The default lease duration is eight days.
- 8. DHCP Messages • All DHCP messages are carried in User Datagram Protocol (UDP) datagrams using the well-known port numbers 67 (from the server) and 68 (to the client). • UDP operates at the Transport Layer of the OSI model and is a low-overhead protocol because it does not use any type of packet acknowledgement.
- 11. DHCP Relay Agent • DHCP relies heavily on broadcast messages. • Broadcast messages are generally limited to the subnet in which they originate and are not forwarded to other subnets. • A DHCP relay agent is either a host or an IP router that listens for DHCP (and BOOTP) client messages being broadcast on a subnet and then forwards those DHCP messages to a DHCP server. • The DHCP server sends DHCP response messages back to the relay agent, which then broadcasts them onto the subnet for the DHCP client. • Using DHCP relay agents eliminates the need to Jagdish
- 12. DHCP Relay Agent
- 13. Automatic Private IP Addressing (APIPA) • If the DHCP client is unable to locate a DHCP server and is not configured with an alternate configuration, the computer configures itself with a 169.254.0.0/255.255.0.0 address. • The auto-configured computer then tests to verify that the IP address it has chosen is not already in use by using a gratuitous ARP broadcast. • If the chosen IP address is in use, the computer randomly selects another address. The computer makes up to 10 attempts to find an available IP address.
- 14. Installing the DHCP Server Role • Adding the DHCP server role is largely wizard-driven via the Server Manager console and allows you to configure basic DHCP settings at the same time that you install the role. • To add DHCP Server Role on a Server Core Installation of Windows Server 2008, use the following command: Start /w ocsetup DHCPServerCore
- 15. Authorizing a DHCP Server • In implementations of DHCP prior to Windows 2000, any user could create a DHCP server on the network, an action that could lead to conflicts in IP address assignments. • In Windows Server 2000 and later, an unauthorized DHCP server (also referred to as a rogue DHCP server) is simply a DHCP server that has not been explicitly listed in the Active Directory Domain Service as an authorized server. • You must authorize a DHCP server in Active Directory before the server can issue leases to DHCP clients.
- 16. Authorizing a DHCP Server • Press Ctrl+Alt+Delete on the Windows Server 2008 computer. • In the DHCP console, right-click DHCP and then click Manage Authorized Servers. • In the Manage Authorized Servers dialog box, select Authorize. • In the Authorize DHCP Server dialog box, key the name or IP address of the DHCP server to be authorized and then click OK. • The computer will list the IP and full computer name and then ask for confirmation. – Click OK to continue.
- 17. DHCP Scope • Determines which IP addresses are allocated to clients. • Defines a set of IP addresses and associated configuration information that can be supplied to a DHCP client. • A scope must be defined and activated before DHCP clients can use the DHCP server for dynamic TCP/IP configuration. • You can configure as many scopes on a DHCP server as needed for your network environment. Atharva
- 18. DHCP Scope • The IP addresses defined in a DHCP scope must be contiguous and are associated with a subnet mask. – If the addresses you want to assign are not contiguous, you must create a scope encompassing all the addresses you want to assign and then exclude specific addresses or address ranges from the scope. – You can create only one scope per subnet on a single DHCP server.
- 19. DHCP Scope
- 20. Available Address Pool • Once a DHCP scope is defined and exclusion ranges are applied, the remaining addresses form what is called an available address pool within the scope. • Pooled addresses can then be dynamically assigned to DHCP clients on the network.
- 21. Superscope • A DHCP superscope is an administrative grouping of scopes that is used to support multinets, or multiple logical subnets (subdivisions of an IP network) on a single network segment (a portion of the IP internetwork bounded by IP routers). • Superscopes contain only a list of member scopes or child scopes that can be activated together.
- 22. DHCP Reservation • Network administrators can use DHCP reservations for DHCP-enabled hosts that need to have static IP addresses on your network. • Reservations must be created within a scope and must not be excluded from the scope. • An IP address is set aside, or reserved, for a specific network device that has the Media Access Control (MAC) address (the hard-coded hexadecimal hardware address associated with a Network Interface Card) associated with that IP address.
- 23. DHCP Reservation • You can find the MAC address with the ipconfig /all command.
- 24. DHCP Reservation
- 25. DHCP Options • DHCP options are additional client- configuration parameters that a DHCP server can assign when serving leases to DHCP clients. • DHCP options are configured using the DHCP console and can apply to scopes and reservations. Mehul
- 26. DHCP Options
- 27. DHCP Options • DHCP options can be assigned to all scopes, one specific scope, or to a specific machine reservation.
- 28. DHCP Options • There are four types of DHCP options in Windows Server 2008: – Server options apply to all clients of the DHCP server. Use these options for parameters common across all scopes on the DHCP server. – Scope options apply to all clients within a scope and are the most often used set of options. Scope options override server options. – Class options provide DHCP parameters to DHCP clients based on type — either vendor classes or user classes. – Client options apply to individual clients. Client options override all other options (server, scope, and class).
- 29. Backup and Restore the DHCP Database • Windows Server 2008 DHCP servers support automatic and manual backups. • To provide fault tolerance in the case of a failure, it is important to back up the DHCP database. – This enables you to restore the database from the backup copy if the hardware fails. • To backup, right-click the server in the DHCP console and click Backup. • To restore the DHCP database, right-click the server and click Restore.
- 30. Summary • DHCP is a simple, standard protocol that makes TCP/IP network configuration much easier for the administrator by dynamically assigning IP addresses and providing additional configuration information to DHCP clients automatically. • Additional configuration information is provided in the form of options and can be associated with reserved IPs to a vendor or user class, to a scope, or to an entire DHCP server.
- 31. Summary • Because DHCP is a key component in your organization, you must manage and monitor it. • DHCP management consists of backing up and restoring the database as well as reconciling, compacting, and, in some cases, removing the database. • APIPA is useful for providing addresses to single-segment networks that do not have a DHCP server.
Editor's Notes
- #8: Be sure students know the default duration length.
- #10: When you troubleshoot DHCP problems, you need to understand that DHCP is a four-step process.
- #13: Again, emphasize the DHCP Relay Agent is needed when you want to centralize DHCP over WAN links.
- #14: If you see a 169.255.X.X address, it cannot find or communicate with a DHCP.
- #16: You must authorize the DHCP server to work with an Active Directory network. Show students how to activate a DHCP server.
- #28: Most likely, you will need to configure the Router (default gateway) settings, DNS and WINS servers.
- #29: If you have multiple scopes, you can use the server DHCP options to set the DNS, WINS and other options in one shot.