Module 4: Planning, Optimizing, and

Troubleshooting DHCP

Overview

Planning a DHCP Strategy

Securing a DHCP Solution

Optimizing DHCP

Troubleshooting DHCP

Lesson: Planning a DHCP Strategy

Multimedia: Planning DHCP Server Placement in the Enterprise

Best Practices for Determining DHCP Server Placement

Choosing a DHCP Infrastructure

Defining Scope Reservations

Selecting DHCP Options

Selecting Option Classes

Guidelines for Planning a DHCP Strategy

Multimedia: Planning DHCP Server Placement in the Enterprise

The objective of this presentation is to plan the placement of DHCP servers in a Windows Server 2003 enterprise network

You will learn how to:

Explain the considerations for a single or multiple DHCP server plan

Determine when to use a single or multiple DHCP server solution to meet organizational requirements

Best Practices for Determining DHCP Server Placement

Best practice DescriptionPlace DHCP servers to minimize traffic across low-speed links

Place servers locally when you have a site that is across a slow link to minimize low-speed traffic

Place DHCP servers to optimize response times

Place DHCP servers to optimize response times for all clients on the LAN

Configure at least one backup server for fault tolerance

You can configure another server by using the 80/20 rule for scopes, configure a DHCP cluster, or use a standby server

Place DHCP server in a screened subnet

Place DHCP servers to provide services for a Web farm

Place DHCP servers close to population

Place DHCP servers on subnets with the highest client population or high lease renewals

Test server placement first in a lab

By testing server placement, you will validate your chosen plan

Choosing a DHCP Infrastructure

LAN 1LAN 1

DHCP server

LAN 2LAN 2

DHCP server

Remote LAN 3Remote LAN 3

DHCP server

Determining the type of DHCP infrastructure to be usedDetermining the type of DHCP infrastructure to be used

CentralizedDistributedMixed infrastructure

CentralizedDistributedMixed infrastructure

Defining Scope Reservations

Create a scope reservation when:Create a scope reservation when:

The device always requires the same address

Multiple DHCP servers service the reserved client

The client has a previously assigned IP address

More than one DHCP server can be reached by a reserved client

The device always requires the same address

Multiple DHCP servers service the reserved client

The client has a previously assigned IP address

More than one DHCP server can be reached by a reserved client

Selecting DHCP Options

DHCP option Description

Routers A preferred list of IP addresses for routers on the same subnet as the DHCP clients

DNS serversIP addresses for DNS name servers that DHCP clients use to resolve names

DNS domainDomain name that DHCP clients should use when resolving names

WINS node type A preferred NetBIOS name resolution method for the DHCP client to use

WINS server IP addresses of primary and secondary WINS servers for the DHCP client to use

Selecting Option Classes

Vendor-defined classes manage DHCP options identified by operating system vendor type

User-defined classes manage DHCP options with common configuration requirements

DHCP ServerDHCP Server

Client 2Client 2Windows 98 Client 1Windows 98 Client 1

Client 3Client 3

Vendor class configuration A

Vendor class configuration C

Vendor class configuration B

Guidelines for Planning a DHCP Strategy

Evaluate the network topologyEvaluate the network topology

Determine which DHCP infrastructure you will useDetermine which DHCP infrastructure you will use

Determine reservationsDetermine reservations

Define DHCP optionsDefine DHCP options

Determine integration issuesDetermine integration issues

Determine the fault tolerance approachDetermine the fault tolerance approach

Practice: Identifying DHCP Planning Issues

In this practice, you will determine a network configuration that meets the needs of the scenario

Lesson: Securing a DHCP Solution

Securing the DHCP Service

Preventing Unauthorized DHCP Servers

Securing DHCP in Screened Subnets

DHCP Administrators

DHCP Users

Active Directory

DHCP Server 1DHCP Server 1 DHCP Server 2DHCP Server 2

Securing the DHCP Service

Authorized ListAuthorized List

DHCP Server 1DHCP Server 1

DHCP Server 2DHCP Server 2

DHCP LogDHCP Log

Preventing Unauthorized DHCP Servers

Active DirectoryActive Directory

DHCP ServiceDHCP Service

Using DHCP servers in Windows 2000

Authorizing DHCP servers in Active Directory

Using DHCP servers in Windows 2000

Authorizing DHCP servers in Active Directory

DHCPINFORM DHCPINFORM

DHCP Server ObjectAuthorized ListDHCP Server ObjectAuthorized List

In authorized list(Startup)

In authorized list(Startup)

Not in authorized list(Shut down)

Not in authorized list(Shut down)

Authorized Windows Server 2003 DHCP Server

Authorized Windows Server 2003 DHCP Server

Unauthorized Windows Server 2003 DHCP Server

Unauthorized Windows Server 2003 DHCP Server

Securing DHCP in Screened Subnets

InternetInternet

External FirewallExternal Firewall

Internal FirewallInternal Firewall

DHCP ServerDHCP Server

Private NetworkPrivate Network

Screened SubnetScreened Subnet

DHCP ServerDHCP Server

Shared Resource ServerShared Resource Server

Web and Shared Resource ServerWeb and Shared Resource Server

Practice: Identifying Authorization Issues

In this practice, you will identify why clients are unable to access network resources.

Lesson: Optimizing DHCP

Improving the DHCP Server

Modifying Lease Duration

Improving the DHCP Server

Factors that impact DHCP server performance include: Factors that impact DHCP server performance include:

The speed of server disk drives.

The amount of RAM available on the DHCP server computer.

The speed of server disk drives.

The amount of RAM available on the DHCP server computer.

Modifying Lease Duration

Option When to use Result

Increase the lease duration

At least 20 percent of IP addresses in scope is availableConfigurations that rarely change on the network

Can reduce DHCP–related network traffic

Reduce the lease duration

Limited number of IP addresses availableClient configurations changeClients move often on your networkRemote access clients

Reduce the chance of running out of addresses to lease

Practice: Modifying Lease Duration to Improve DHCP Performance

In this practice, you will modify lease duration to improve DHCP performance

Lesson: Troubleshooting DHCP

Defining DHCP Problems

DHCP Troubleshooting Tools

Troubleshooting Common DHCP Issues

How to Troubleshoot DHCP Issues

Defining DHCP Problems

Is service operating

properly?

Are scopes configured

correctly?

Are leases available

for proper scopes?

Is the client properly connected

to the network?

Are you getting a

lease?

Where is the lease originating?

Are relay agents and routers

configured properly?

Are packets routing between

subnets?

How many clients are

affected?

Significant number ofclients affected

Only oneclient affected

Server-side issue

Client-side issue

Infrastructure issue

DHCP Troubleshooting Tools

Tool Purpose

Network Monitor For viewing packet-level information

DHCP Audit Log

Log DHCP events and critical errors

IPconfigFor generating DHCP traffic for testing purposes and reviewing current configuration

Troubleshooting Common DHCP Issues

Client-side problems

Server-side problems

Relay agent problems

DHCP database problems

How to Troubleshoot DHCP Issues

In this procedure, you will learn how to troubleshoot DHCP issues

Practice: Troubleshooting DHCP Issues

In this practice, you will determine DHCP troubleshooting steps

Lab A: Planning a DHCP Strategy

Exercise 1: Planning the DHCP Solution

Lab B: Troubleshooting DHCP Issues

Exercise 1: Optimizing DHCP Redundancy for Multiple Subnets

Exercise 2: Troubleshooting DHCP Problems