MCTS Guide to Microsoft Windows Server 2008 Network Infrastructure Configuration Chapter 4 Installing and Configuring the Dynamic Host Configuration Protocol

Objectives Discuss the basics of Dynamic Host Configuration Protocol (DHCP) Describe the components and processes of DHCP Install DHCP in a Windows Server 2008 environment Configure the DHCP server Administer DHCP on clients and servers Troubleshoot DHCP

Basics of DHCP DHCP – Layer 4 protocol that uses User Datagram Protocol (UDP) datagrams for communication – Defined by Request for Comment (RFC) 2131 – Clients use UDP port 68 to send and receive DHCP broadcast communication – Servers use UDP port 67 to send and receive DHCP broadcast communication

Exploring DHCP Components and Processes DHCP lease – Defines the amount of time, or the duration, that an IP address is loaned to a DHCP client Lease duration – Amount of time a client keeps an IP address before releasing it DHCP scope – A range of IP addresses and related configuration information available by request from a DHCP client

Exploring DHCP Components and Processes (continued) DHCP options – IP address – Subnet mask – Default gateway – Primary and secondary DNS servers – DHCP lease expiration DHCP reservations – Allow you to assign a specific IP address to a DHCP client without statically configuring the device with IP information

DHCP Communication Processes DHCP message types – DHCPDiscover, DHCPOffer – DHCPRequest, DHCPAck – DHCPNack, DHCPDecline Initial lease request – Clients make these requests if they do not have a current lease on a scope Lease renewals – Intervals: Renewal time value and Binding time value

DHCP Communication Processes (continued) Changing subnets – When a client moves to a new subnet, it cannot use its current lease because the IP information does match the new network configuration

Using DHCPv6 IPv6 clients – Use DHCP to receive IP address and configuration information from an IPv6 router on their network Implementing DHCPv6 requires – Configuring your router to forward all autoconfiguration requests to an available DHCPv6 server – Disabling stateless mode on your Windows Server 2008 DHCP servers

Installing DHCP in a Windows Server 2008 Environment DHCP Server role – Requires minimal server resources – Starts the DHCP Server service – Installs the files needed for the DHCP database – Initializes the DHCP console on the local system

Installing DHCP in a Windows Server 2008 Environment (continued) DHCP database – Based on the Joint Engine Technology (JET) storage engine – Database size is based on the number of client requests it receives DHCP Server service – Installed with the DHCP Server role DHCP Server console – The GUI tool for managing DHCP on Windows Server 2008

Authorizing DHCP In Active Directory domains – DHCP servers must be authorized before they can begin supplying IP addresses In Windows Server 2008 – You are prompted for credentials during installation if your server is a member of a domain

Configuring the DHCP Server After installing the DHCP role – You need to configure DHCP for its initial use DHCP – Requires at least one DHCP scope to issue IP addresses for network clients

Configuring Exclusions Exclusions are created so that: – Static IP addresses for devices such as routers, printers, or other network devices are not assigned Common practice – Create exclusionary ranges at the beginning and end of a scope range

Configuring Options Options – Allow you to quickly and easily provide DHCP clients with updated configuration information If you are using the default lease duration of eight days – Could take up to four days before clients receive the new DHCP options you deploy

Creating Reservations Reservations – Used in DHCP to give a DHCP client a static IP address without manually configuring the address on the client

Using netsh Syntax for creating a DHCP reservation netsh Dhcp Server Scope add reservedip c40fb6a MSN- SRV-150 Syntax for creating a DHCP exclusionary range netsh Dhcp Server Scope add excluderange

DHCP Client Configuration DHCP Client service – Responsible for the DHCP configuration process on a client machine Fault tolerance and DHCP – Microsoft recommends using an 80/20 rule for splitting scopes between two servers for fault tolerance – 80/20 rule 80 percent of a scope’s total IP range is hosted on your primary DHCP server, while the remaining 20 percent is hosted on your secondary DHCP server

DHCP Administration Monitoring reliability and performance – Monitoring allows you to determine the current state of DHCP – Reliability and Performance Monitor Used to create a real-time picture of what is happening on the local or remote server

Monitoring Reliability and Performance (continued) DHCP console statistics – Server statistics: broader and provide a more comprehensive picture of the status of your DHCP server – Scope statistics: display information about each scope

Monitoring Reliability and Performance (continued) DHCP audit log – Lists detailed information about events occurring on a specific day, including Event ID, Date and time Event description, IP address Host name, MAC address

Backup and Recovery Automatic backup – Windows Server 2008 performs an automated backup of the DHCP database every 60 minutes Manual backup – Stored in the %systemroot%\systemroot\dhcp\backup folder Restoring the DHCP database from a backup – You can restore a DHCP database from an offline backup when you are building a new DHCP server

Troubleshooting DHCP Reconciling the database – Validates the DHCP database by comparing it with the Registry values of the operating system to verify that the database contains the most current data

Verifying DHCP Services To determine the running services on a system – Enter the net start command at a command prompt To stop a running service net stop “DHCP Server” or “DHCP Client” net start “DHCP Server” or “DHCP Client”

Troubleshooting DHCP Clients: IPconfig ipconfig – Can be used to renew the current IP address and configuration information and to release the current IP address Entering the ipconfig /release command – Issues the DHCPRelease message to the server currently holding the IP address lease for a client

Summary Information provided by a DHCP server includes: – Leases, scopes, and options For DHCP to function properly in a routed network: – A DHCP relay agent or an RFC 1542–compliant router needs to be in place to pass along DHCP messages DHCP – Uses a standard set of messages for communicating between DHCP clients and DHCP servers

Summary (continued) Common communication processes – Initial lease requests, lease renewals, and changing subnet renewals All data in DHCP is stored in the DHCP database Only DHCP servers in an Active Directory domain need to be authorized After DHCP is installed – You must configure scopes for DHCP clients to receive addresses

Summary (continued) DHCP console or netsh – Can be used to perform all configuration tasks DHCP – Uses exclusions to prevent making the IP addresses of statically assigned devices available in an IP scope range To monitor DHCP – Use Performance Monitor, DHCP statistics, and the DHCP audit log