AZ-800 Administering Windows Server Hybrid Core Infrastructure Exam

Configure and Validate DHCP Failover

DHCP failover provides high availability for IP address assignment by setting up two servers that can back each other up. This feature is vital in a hybrid environment where on-premises and Azure resources need continuous connectivity. By using failover, you achieve continuous IP address distribution even if one server goes offline. It ensures client devices always have valid network configurations.

To begin the setup, you need an Azure virtual machine that will host the secondary DHCP server. On this VM, deploy the DHCP role and adjust network adapter settings to allow request forwarding. Use the weakhostreceive and weakhostsend commands to enable packet reception and transmission on both the primary and loopback adapters:

• netsh int ipv4 set int <adapter index> weakhostreceive=enabled
• netsh int ipv4 set int <adapter index> weakhostsend=enabled
  These steps prepare the server to handle DHCP traffic from multiple network sources.

Next, install the DHCP role on both on-premises and Azure servers if not already present. Then configure a DHCP relay agent on your on-premises router or switch to forward client requests to the Azure server. Key tasks include:

• Installing the DHCP server service
• Setting up authorized scopes on both servers
• Adding relay agent IP addresses pointing to Azure DHCP
  These tasks ensure requests reach the correct server and that scopes stay synchronized.

Once configuration is complete, choose a failover mode that fits your needs: load-balancing or hot-standby.

• Load-balancing mode splits client requests evenly between the two servers.
• Hot-standby mode keeps one server as primary and uses the secondary only if the primary fails.
  Selecting the right mode guarantees that your network can tolerate server failures or heavy loads without dropping requests.

Finally, you must monitor the replication health and perform simulated failover tests. Check event logs and use PowerShell cmdlets to verify that scope lists and leases are properly synced. Run a test by disabling the primary server to see if the secondary takes over without service interruption. Regular monitoring and testing keep your DHCP high availability solution reliable and resilient.

Conclusion

In this section, you learned how to set up DHCP failover between on-premises and Azure servers for continuous IP address distribution. You saw how to configure network adapters, install DHCP roles, and use a DHCP relay agent. You also explored failover modes—load-balancing and hot-standby—and the importance of monitoring replication health. Finally, simulated failover tests help confirm that your configuration maintains network connectivity if a server goes down. Implementing these steps ensures a robust, highly available DHCP infrastructure in hybrid environments.