How to Configure DHCP Failover Cluster on Windows Server 2012

All of you know that we didn't have any Failover option for DHCP in the past. So most of us created different DHCP scopes for one IP range on different servers. This was needed to get a partly redundant DHCP option. This was working but any changes for reservations, scope changes or configuration changes must be done manually or with scripts. This took time or wasn't really successful. 

With Windows Server 2012, we get a real Failover cluster including configuration replication. Please notice, the only available options are load balanced and hot standby. I will explain you later when you should use which option. So let us start to configure our cluster. 

Steps

1. You need to install the first DHCP Server and configure the DHCP Scope. This DHCP Server has to be Windows Server 2012 Standard or Datacenter.   

2. Next install a new server with Windows Server 2012 or take one other free server from your existing Windows Server 2012 Systems as Windows Server 2012 DHCP Failover Cluster partner. In my case I installed a fresh Windows Server 2012 VM as Failover Partner.  

3.  Now your could add the new node to your Server Manager, if you want to manage the Server remote. You can also configure the Failover Setup without this, but it helps to manage both Servers later.

4. When the DHCP role was installed correct on the second host and you added the server for management to your management host, than you should see both systems under DHCP. 


Figure 1: DHCP Server

5. In the next step open the DHCP MMC.


Figure 2: DHCP MMC

6. In the DHCP MMC please add the second DHCP Server first. You can do this via right click on "DHCP" and than "Add Server".


Figure 3: Add Server

7. Now you should see both DHCP Servers in the list.  

12. In the next step we authorize the DHCP server to our Domain.

13.  Now click right on the scope that you want to cluster and select "Configure Failover". 


Figure 4: Configure Failover

14. When the Wizard starts, you see the Scope that can be clustered. 


Figure 5: Wizard starts

If you see no available Scope, you have to check if DHCP Service is up, DHCP Server is complete configured and there are no issues with DNS and ADDS.  

15. Next step is to select the failover partner.


Figure 6: Failover partner

16. When you authorized the second DHCP server before, you see it in the second list. Otherwise you have to select "This Server:" and "Browse".


Figure 7: Server and Browse

17.  Now you type in the name of the server.


Figure 8: Type pf the server

18. When you entered the name click "Check Names". When the wizard found the server, click "ok". 


Figure 9: Check Names

19. Click "ok" and the server will attached to DHCP MMC. 


Figure 10: Attached Server

20. Now you see the selected Server with complete FQDN in the Pattern Server field. 


Figure 11: FQDN in the Pattern Server field

Click "Next" to go on.  

21. Now you have to set the cluster configuration.

Load Balanced:


Figure 12: Cluster configuration

Relationship Name: Name of your Failover Cluster

Maximum Client Lead Time: Defines the amount of time the surviving server will wait before assuming control of the entire scope.

Mode: Load Balanced - When the cluster is configured in Load Balance mode, this results in an active-active setup of the two DHCP Servers. You should use when you have big networks with many clients or you want to deploy the cluster in different branch offices.

Load Balance Percentage: Means how the work is split up between both hosts. The percentages together can only be 100%. The node with the highest percentage gets the highest workload.

State Switchover Interval: automatically change state to partner down after <time>.

Enable Message Authentication: enables authentication from cluster nodes.

Shared Secret: Validation Password that identifies the node as partners against each other.  

Standby:


Figure 13: Name of your Failover Cluster

Relationship Name: Name of your Failover Cluster

Maximum Client Lead Time: Defines the amount of time the surviving server will wait before assuming control of the entire scope.

Mode: Hot Standby - When the cluster is configured in Hot Standby mode, one node is active and the second is standby and will only take over when the primary DHCP Server fails. You should use when you need the partner as fault tolerance.

Addresses reserved for standby server: Means how many address the standby can lease before he takes over the entire scope and becomes active.

State Switchover Interval: automatically change state to partner down after <time>.

Enable Message Authentication: enables authentication from cluster nodes.

Shared Secret: Validation Password that identifies the node as partners against each other.  

22. After clicking "Next" you see a short summary of your configuration. 


Figure 14: Name of your Failover Cluster


Figure 15: Name of your Failover Cluster

23.  Klick "Finish" and the cluster configuration starts.  

24. In the DHCP MMC click right on the Scope and force a replication by clicking on "Replicate Failover Scope" and than on the refresh  button or press F5.


Figure 16: Replicate Failover Scope

25. On the failover node check the config. If the config is right your finished. 


Figure 17: On the failover node check the config