DHCP Fail-over on Windows Server 2019

https://www.youtube.com/watch?v=lf4q943u_5s

To configure a failover relationship

In DHCP2, open the DHCP console, right-click the DHCP scope Contoso-scope1, and then click Configure failover.
In the Configure Failover wizard, click Next.
In Specify the partner server to use for failover, type the dhcp1.contoso.com next to Partner Server, and then click Next.
In Create a new failover relationship, type a name next to Relationship Name, or accept the default name displayed (dhcp2.contoso.com-dhcp1.contoso.com).
Next to Shared Secret (e.g., secret), type a shared secret for this failover relationship.
Change the value next to Maximum Client Delivery Time to 0 hours and 1 minute.Important Maximum Client Lead Time (MCLT) is the grace period provided to a DHCP client after the expiration of a DHCP lease. The MCLT is transmitted from the primary server to the secondary server in the CONNECT message and is the longest period of time a server can extend the lease agreement for a client beyond the time known to the partner server. The 1-minute MCLT value used here is for test lab purposes only to request lease renewal by the client. In a production environment, you must use a longer MCLT, such as 1 hour.
Review the options in the drop-down menu next to Mode. You can select either Load balance or Active standby. By default, Load balance mode is selected.
Click Next, and then click Finish.
Verify that the failover configuration was successful, and then click Close.
In DHCP1, refresh the DHCP console, and verify that the same DHCP scope configuration that was available in DHCP2 is now available in DHCP1.

View or edit the properties of a failover configuration

After you configure a failover relationship on the DHCP server, the details of the failover relationship are displayed in the DHCP console.

To view or edit the properties of a failover relationship

In DHCP1 or DHCP2, in the DHCP console, right-click the DHCP scope Contoso-scope1, and then click Properties.
Click the Failover tab, and then review the information that is displayed. Verify that Normal is displayed next to This Server Status and also next to Partner ServerStatus.
Note that you can edit or delete the failover relationship.
Click Edit and review the editable properties of the failover relationship.
Leave the dialog box open for the following procedure.

Edit properties of the failover relationship and demonstrate load balancing

To demonstrate dynamic load balancing properties of the failover relationship, the load balancing percentage will be changed for an active DHCP scope.

To edit properties of the failover relationship and demonstrate load balancing

On Client1, click Windows PowerShell and type the following command. Copyipconfig /all
In the command output, note the DHCP server that is providing IP address configuration to Client1. The IP address of the DHCP server is displayed next to DHCP Server.
In the View/Edit DHCP1 or DHCP2 Failover Relationship dialog box that opens in the previous procedure, change the values under Load Balanced Mode next to Local Server and Partner Server so that 100% of them are assigned to the DHCP server that does not provide an IP address to Client1. The value of the server that is providing the IP address to Client1 will be 0%.
Click OK twice, wait until the current DHCP lease expires on Client1, and then type ipconfig /all at the Windows PowerShell prompt.
Note that the DHCP server that provides IP address configuration to Client1 changes to the server to which you assign 100% weight in load-balancing mode.

Edit the properties of a failover relationship and show hot standby mode

To show hot standby mode, the DHCP Server service on one of the failover partners is stopped.

To edit the properties of a failover relationship and show hot standby mode

In DHCP1 or DHCP2, in the DHCP console, right-click the DHCP scope Contoso-scope1, and then click Properties.
Click the Failover tab.
Click Edit, and then select Hot Standby Mode.
Depending on the DHCP server that you configure, the local server is assigned an Active or Pending status. The status is displayed next to Role of this server.TipThe server that is actively assigned in hot standby mode is the server that you used to create the failover relationship.
Click OK two times, and then wait 2 minutes for the DHCP lease on Client1 to renew.
On Client1, type ipconfig /all at the Windows PowerShell prompt and verify that the server assigned as Active provides Client1 with a configuration of IP addresses.
In the DHCP console on the DHCP server, which is marked as Active for the hot standby failover relationship and is providing an IP address to Client1, right-click the server name, point to All Tasks, and then click Stop.
Verify that the DHCP service is stopped on the active DHCP server.
Wait for the DHCP lease to be renewed on Client1, type ipconfig /all at the Windows PowerShell prompt, and verify that the standby DHCP server has provided Client1 with an IP address.

The end

DHCP failover, clustering, or a split scope provides high availability of DHCP services without the hassles of DHCP. The benefits of DHCP failover include the following:

Simple: A wizard is provided to create DHCP failover relationships between DHCP servers. The wizard automatically replicates scopes and settings from the primary server to the failover partner.
Flexible: DHCP failover can also be configured for load balancing with client requests that are distributed between both DHCP servers in a failover relationship, depending on the values you choose.
Hassle-free: DHCP servers share lease information and allow one server to assume responsibility for servicing clients if the other server is unavailable. DHCP clients can maintain the same IP address when the lease is renewed, even if the lease agreement is issued by a different DHCP server.

Arif Akyüz
Content Producer & Cyber Security Expert
[email protected]