White Paper DHCP Clustering and Migration

DHCP Clustering in windows Server 2012 & Migrating DHCP Database from Windows Server 2003 to 2012 DHCP Server.

White Paper

Sreejith Application Technology

DHCP Clustering in windows Server 2012

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Abstract This document explains about how to configure DHCP Clustering in windows Server 2012 whichensures high availability of DHCP Services. This document also helps in migrating DHCP database from environments which have windows Server 2003 running to windows Server 2012.

About the Domain Dynamic Host Configuration protocol Service assigns IP Address to clients which will help workstations to communicate in the LAN. DHCP Cluster will ensure that Clients will get the service all the time without any downtime.

CONTENTS INTRODUCTION ........................................................................................................................................ 3

DHCP FAILOVER OVERVIEW.................................................................................................................4

DHCP Deployment Steps...4 DHCP Failover Terminology..........................................10

DHCP DATABASE MIGRATION FROM 2003 OS TO 2012 OS .........................................................11

ACKNOWLEDGEMENTS ........................................................................................................................12

REFERENCES ............................................................................................................................................12


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Introduction:

Using Dynamic Host Configuration Protocol (DHCP) Server service, the process of configuring TCP/IP on DHCP clients is automatic. For ensuring High availability of the service, we can configure DHCP Clustering in Windows Server 2012 Server. DHCP Clustering will ensure that if one Server goes down, other server will be serving DHCP Service for clients.


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DHCP Failover Overview:

DHCP failover in Windows Server 2012 is a new feature that enables two Microsoft DHCP servers to share service availability information with each other, providing DHCP high availability. DHCP failover works by replicating IP address leases and settings in one or more DHCP scopes from a primary DHCP server to a failover partner server. All scope information is shared between the two DHCP servers, including active leases. This enables either DHCP server to assume responsibility for DHCP clients if the other server becomes unavailable. Prerequisites for configuring DHCP Failover.

Both DHCP servers in a DHCP failover relationship must be running Windows Server 2012 or a later operating system

Both computers participating in a DHCP failover relationship must have the DHCP Server role installed and running.

DHCP servers can be on the same network or on different networks. The network connection between DHCP failover partners must be uninterrupted. Both of the servers must be able to communicate properly

At least one IPv4 DHCP scope must be configured on the primary DHCP server.

Deploying DHCP Failover:

Right Click the Scope on which we want to configure Failover. Then click

Configure Failover


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Select all the scopes which we would need to configure for Failover as shown below.

Set a Relationship name which should identify the Scope details, Maximum Client Lead Time, Mode and State Switch over Interval. After specifying all these parameters, click next and add the partner server details as given below


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Select the partner Server & click next.


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Verify the settings and Click Finish. DHCP Scope Failover is completed.


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DHCP Failover Terminology:

Maximum client lead time: The maximum amount of time that one server can extend a lease for a DHCP client beyond the time known by the partner server. It also determines the amount of time that a server in a failover relationship will wait in partner down state before assuming control over the entire IP address range.

Reserve percentage: In a failover relationship configured in hot standby mode, administrators can specify a percentage of the address range of the scope as reserved for the hot standby server. A number of addresses, in proportion to the percentage value configured, are assigned to the hot standby server. The hot standby server will use these addresses to service new clients after the primary server goes down, during the time interval before the standby server assumes control over the entire IP address range of a scope.

State switchover interval: If automatic state transition is enabled, a DHCP server in communication interrupted state will automatically transition to partner down state after a defined period of time. This period of time is defined by the state switchover interval.

Hot Standby Mode: In hot standby mode, two servers operate in a failover relationship where an active server is responsible for leasing IP addresses and configuration information to all clients in a scope or subnet. The partner server assumes a standby role, with responsibility to issue leases to DHCP clients only if the active server becomes unavailable. Hot standby mode is ideal for scenarios where the failover partner is only intended to be used temporarily when the active server is unavailable.

Load Balance Mode:Load balance mode is the default mode of deployment. In this mode, two DHCP servers simultaneously serve IP addresses and options to clients on a given subnet. DHCP client requests are load balanced and shared between the two DHCP servers. The default load balancing ratio between the two servers is 50:50, but this can be customized to any ratio from 0 to 100%. This is done based on an algorithm which uses Mac Address of workstations for serving IP Address.


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DHCP Database Migration from 2003 DHCP to 2012 DHCP Server

Overview:

For migrating environments running with windows Server 2003 DHCP Server, we would need to export the live DHCP Database first. Backup and restore of DHCP database wont be successful in this scenario.

We can use Netsh utility for exporting the DHCP live database. Post exporting the database, we need to copy the database on to the destination server and has to import it back. Below are the commands for doing the same.

Migration Steps:

On the Windows 2003 DHCP server, navigate to a command prompt and type the command in the below order

Type Netsh and hit enter

Type DHCP and hit enter

Type server \\Name or IP Address from command prompt.

Then type export c:\w2k3DHCPdb all

Then copy paste the exported data to windows 2012 Server on which we would need to import it. Once copying is done, please follow the below commands for importing the database.

Before executing the below steps, please ensure Destination server must have DHCP Role installed and the windows Server 2003 is not reachable in network.

On the designated DHCP server, stop the DHCP Services.

Delete the DHCP.mdb file under c:\windows\system32\DHCP folder.

Start the DHCP Service and execute the below commands

Navigate to command prompt and type Netsh and hit enter

Type DHCP and hit enter

Type server \\Name or IP Address and hit enter

Type import c:\w2k3DHCPdb

Close the command prompt when completed.

Restart the DHCP Services.


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We would be able to see all the data which was available on windows Server

2003 Server

Conclusion:

1. Windows Server 2012 Failover feature helps administrators in ensuring high

availability of DHCP Service for clients.

2. Using Netsh utility we can migrate the DHCP Database from windows Server

2003 Server to 2012 DHCP Server without any down time for end users.

Acknowledgements

Thank to Trivandrum IS team for helping in doing the DHCP Configuration and also in preparing the document.

References

[1] Microsoft Site (Technet) [2] https://nzmct.wordpress.com/2012/10/16/dhcp-resiliency-in-windows-server-2012/

Introduction:DHCP Failover Overview:Deploying DHCP Failover:

DHCP Failover Terminology:Maximum client lead time: The maximum amount of time that one server can extend a lease for a DHCP client beyond the time known by the partner server. It also determines the amount of time that a server in a failover relationship will wait in partner ...Reserve percentage: In a failover relationship configured in hot standby mode, administrators can specify a percentage of the address range of the scope as reserved for the hot standby server. A number of addresses, in proportion to the percentage val...State switchover interval: If automatic state transition is enabled, a DHCP server in communication interrupted state will automatically transition to partner down state after a defined period of time. This period of time is defined by the state switc...Hot Standby Mode: In hot standby mode, two servers operate in a failover relationship where an active server is responsible for leasing IP addresses and configuration information to all clients in a scope or subnet. The partner server assumes a standb...Load Balance Mode:Load balance mode is the default mode of deployment. In this mode, two DHCP servers simultaneously serve IP addresses and options to clients on a given subnet. DHCP client requests are load balanced and shared between the two DHCP se...DHCP Database Migration from 2003 DHCP to 2012 DHCP ServerOverview:For migrating environments running with windows Server 2003 DHCP Server, we would need to export the live DHCP Database first. Backup and restore of DHCP database wont be successful in this scenario.We can use Netsh utility for exporting the DHCP live database. Post exporting the database, we need to copy the database on to the destination server and has to import it back. Below are the commands for doing the same.Migration Steps:On the Windows 2003 DHCP server, navigate to a command prompt and type the command in the below orderType Netsh and hit enterType DHCP and hit enterType server \\Name or IP Address from command prompt.Then type export c:\w2k3DHCPdb allThen copy paste the exported data to windows 2012 Server on which we would need to import it. Once copying is done, please follow the below commands for importing the database.Before executing the below steps, please ensure Destination server must have DHCP Role installed and the windows Server 2003 is not reachable in network.On the designated DHCP server, stop the DHCP Services.Delete the DHCP.mdb file under c:\windows\system32\DHCP folder.Start the DHCP Service and execute the below commandsNavigate to command prompt and type Netsh and hit enterType DHCP and hit enterType server \\Name or IP Address and hit enterType import c:\w2k3DHCPdbClose the command prompt when completed.Restart the DHCP Services.We would be able to see all the data which was available on windows Server 2003 ServerConclusion:Windows Server 2012 Failover feature helps administrators in ensuring high availability of DHCP Service for clients.Using Netsh utility we can migrate the DHCP Database from windows Server 2003 Server to 2012 DHCP Server without any down time for end users.AcknowledgementsReferences

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White Paper DHCP Clustering and Migration