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70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network, Enhanced Chapter 5: Planning, Configuring, And Troubleshooting DHCP. Objectives. Understand the DHCP lease and renewal process Plan DHCP for small or large networks Install DHCP Authorize a DHCP server
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70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network, EnhancedChapter 5: Planning, Configuring, And Troubleshooting DHCP
Objectives • Understand the DHCP lease and renewal process • Plan DHCP for small or large networks • Install DHCP • Authorize a DHCP server • Configure a DHCP server with scopes, superscopes, and more • Manage and monitor a DHCP server • Troubleshoot DHCP 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
The DHCP Process • On a network DHCP delivers IP addressing information automatically: • To client computers • Servers and other devices such as printers • Using DHCP reduces the amount of time spent configuring individual computers on the network 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Leasing an IP Address • A client computer that is configured to use DHCP must obtain a lease for an IP address • The process to lease an address is composed of four packets: • DHCPDISCOVER • DHCPOFFER • DHCPREQUEST • DHCPACK 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Leasing an IP Address (continued) 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Renewing An IP Address • An IP address is permanent or timed • A permanent address is never reused for another client • A timed lease allows clients to use an IP address for a specified period of time • A client can initiate the release of an IP address before the lease time has expired by using the command ipconfig/release 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Renewing An IP Address (continued) 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Planning DHCP • When planning how to implement DHCP, you must first consider whether it is a small or large network • A small network with a single subnet: • Uses only hubs and switches (no router) • Uses a single DHCP server to service all clients without any special configuration 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
When You Have a Large Network • Large networks with more than one subnet use routers to move packets between the subnets • DHCP relays or multiple DHCP servers must be configured • Having several DHCP servers makes management very complex because each server is managed separately 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
When You Have a Large Network (continued) 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
DHCP Relay • A DHCP relay allows DHCP communication across routers • Using DHCP relays can drastically simplify the implementation of DHCP because it reduces or eliminates the need for multiple DHCP servers • DHCP relay receives broadcast DHCP packets from clients and forwards them as unicast packets to a DHCP server • DHCP relay must be configured with the IP address of the DHCP server to deliver the unicast packets 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
DHCP Relay (continued) 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Fault Tolerance • A fault-tolerant DHCP system can be designed using multiple DHCP servers, if no two servers hand out the same range of addresses at the same time • When creating a fault-tolerant DHCP infrastructure, you can implement: • A hot spare DHCP server • Multiple DHCP servers • Clustering 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Hot Spare DHCP Server • A hot spare is a spare server preconfigured and ready to use • The main advantage is simplicity • Disadvantages are: • IP address conflicts • Synchronizing information between two servers • Lag time between recognizing that the initial DHCP server is down and getting the hot spare DHCP server up and running 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Multiple DHCP Servers • Multiple DHCP servers can service the same subnet as long as they don’t lease the same range of IP addresses • Multiple DHCP servers are effective when DHCP relay is used • If two DHCP servers are configured on a single subnet, they need to have IP address ranges of equal size • If a DHCP relay is used between two DHCP servers, the address range needs to be split as follows: • 75% to 80% of the addresses on the local DHCP server • 20% to 25% of the addresses on the remote DHCP server 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Clustering • When clustering is used for DHCP, multiple servers on the same subnet have DHCP installed, but it is active on only one server at a time • When DHCP fails on one server, it is automatically started on the next server • Servers configured in a cluster can share disk space on an external storage system; this allows them to share configuration information for services • Main disadvantage of clustering is the complexity involved in setting it up 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Installing DHCP • DHCP is a standard service that is included with Windows Server 2003 • Not installed as part of the installation • Must be added later using Add or Remove Programs 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-1: Installing DHCP • The purpose of this activity is to install DHCP on Windows Server 2003 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
DHCP Server Authorization • Control over DHCP is important: an unauthorized DHCP server can hand out incorrect IP addressing information to hundreds of client computers quickly • To exercise control over DHCP, Windows Server 2003 must be authorized to start the DHCP Service • Authorization of a DHCP server takes place in Active Directory with the DHCP Management snap-in 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-2: Starting an Unauthorized DHCP Server • The purpose of this activity is to view the results of starting an unauthorized DHCP server 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-3: Authorizing a DHCP Server • The purpose of this activity is to authorize a DHCP server in Active Directory 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Configuring DHCP • Configuration of DHCP is normally done with the DHCP Management snap-in • The DHCP elements that can be configured include: • Scopes • Superscopes • Multicast scopes • Reservations • Additional options • Vendor and User classes 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Scopes • Use a scope to define a range of IP addresses for the DHCP server to hand out to client computers • Each scope is configured with: • Name • Starting IP address • Ending IP address • Subnet mask • Lease duration • Description • Can also configure exclusions for the scope 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-4: Creating a Scope • The purpose of this activity is to create a scope to distribute IP addresses to client computers 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-5: Activating and Testing a Scope • The purpose of this activity is to activate a DHCP scope, and then test it with a partner 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Superscopes • A superscope combines multiple scopes into a single logical scope • Can do this when a single physical part of the network has two subnets on it 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Superscopes (continued) 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-6: Configuring a Superscope • The purpose of this activity is to combine two scopes into a single logical unit using a superscope 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-7: Deleting a Superscope • The purpose of this activity is to delete a superscope and one of the scopes inside it 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Multicast Scopes • A multicast scope delivers multicast addresses to applications that require it • When you create a multicast scope, you configure: • Start and end IP addresses • TTL (Time to Live) • Exclusions • A lease duration • Activation 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-8: Creating a Multicast Scope • The purpose of this activity is to create a multicast scope to deliver multicast addresses to applications 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Reservations • Use a reservation to hand out a specific IP address to a particular client computer or device on the network • Reservations are beneficial with firewalls • Reservations are created based on the MAC address of the network card on the client workstation 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-9: Creating and Testing a Reservation • The purpose of this activity is to create a DHCP reservation and test it with a client 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Additional Options • DHCP can hand out a variety of other IP configuration options such as: • Default gateway • DNS server • WINS server and many more • These options can be configured for the entire server, a scope, or a single reservation 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-10: Setting Server Options • The purpose of this activity is to set the DNS server option for a DHCP server 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-11: Setting Scope Options • The purpose of this activity is to set the default gateway in the scope options 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Vendor and User Classes • Can use Vendor and User classes to differentiate between clients within a scope • Vendor classes are client categories based on the operating system being used • User classes are client categories defined based on how a client is connected to the network or by the network administrator 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Vendor and User Classes (continued) • The DHCP server included with Windows Server 2003 has three predefined User classes : • Default User Class • Default Routing and Remote Access Class • Default BOOTP Class 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Managing and Monitoring DHCP • To manage and monitor your DHCP server you can perform the following tasks: • Backing up and restoring DHCP databases • Reconciling scopes • Viewing statistics • Enabling DHCP audit logging • Enabling conflict detection • Modifying file paths Changing bindings • Viewing DHCP events in Event Viewer • Viewing DHCP statistics in the Performance snap-in 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Backing Up and Restoring DHCP Databases • The DHCP Service has the following files: • The database holding the addressing information that has been assigned to client computers • Temporary database files only present during maintenance operations • Transaction logs of changes to the DHCP database • Checkpoint file that keeps track of which entries in the log files have been applied to the database 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Reconciling Scopes • The DHCP database holds a summary version and a detailed version of the IP address lease information for a server • If there is a discrepancy between the two versions of information, you must reconcile the scope to synchronize the information 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Viewing Statistics • The Windows Server 2003 DHCP Service automatically tracks statistics that you can view • To view these statistics, right-click the server or scope, and click Display Statistics 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Enabling DHCP Audit Logging • DHCP audit logs keep detailed information about DHCP server activity • Logging is enabled by default and keeps up to seven audit logs • These logs help troubleshoot why a DHCP server is not functioning as expected 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Enabling Conflict Detection • Conflict detection prevents a DHCP server from creating IP address conflicts • When conflict detection is enabled, a DHCP server pings an IP address before it is leased to a client computer • This ensures that even if another device is statically configured with that IP address, it is not leased 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Modifying File Paths • Can control the location of the audit log file, the DHCP database, and the automatic backup directory • Leave these files in their default locations • To modify the paths to where these files are stored, access the properties of the DHCP server in the DHCP Management snap-in 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Changing Bindings • If a DHCP server has multiple network cards, you can choose which network cards the DHCP Service is bound • DHCP server hands out IP addresses only through a network card to which the DHCP Service is bound • Bindings are controlled in the Advanced tab of the server Properties in the DHCP Management snap-in 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Viewing DHCP Events in Event Viewer • In addition to audit logging, some summary information generated by the DHCP Service is placed in the system event log • Can view these events using Event Viewer 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-12: Viewing DHCP Events in Event Viewer • The purpose of this activity is to see the events placed into the system log by the DHCP Service 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Activity 5-13: Removing DHCP • The purpose of this activity is to remove the DHCP Server service from your server 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network
Viewing DHCP Statistics in the Performance Snap-in • When DHCP is installed on Windows Server 2003, new objects and counters are added to the Performance snap-in • Can monitor these counters to track the performance of DHCP over time • If you establish an initial benchmark of DHCP performance under average conditions, then you can tell if something is functioning abnormally later 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network