Configuring the DHCP Server
In this blog post, we will configure the DHCP role on the RRAS server. This will allow computers to receive IP addresses automatically. The idea is that servers will have static IPs assigned, while client computers will have dynamic IPs.
Additionally, we will prepare a standby DHCP server on the Domain Controller.
The Idea of DHCP Failover Stand-by Server
What is DHCP Failover?
DHCP failover is a feature that enables two DHCP servers to share service availability and lease information, providing high availability for DHCP services. In other words, it ensures that if one DHCP server becomes unavailable, the other server can seamlessly take over the responsibility of providing IP addresses to clients.
There are two DHCP Failover modes:
- Hot standby mode: In this mode, two servers operate in a failover relationship. The 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, issuing leases to DHCP clients only if the active server becomes unavailable. Hot standby mode is ideal for scenarios where the failover partner is intended to be used temporarily when the active server is unavailable.
- Load Balance Mode: In this mode, both DHCP servers are active simultaneously, and the load is shared between them. Client requests are distributed between the two servers. Redundancy for DHCP is also provided in a load-balancing configuration. If a DHCP client’s assigned server does not respond, the client can renew its lease with the failover partner server.
Hot Standby mode:
Load Balance:
We will use Hot standby mode. In the hot standby failover mode, there are two DHCP servers:
- Active server: is responsible for handling DHCP requests and leases.
- Standby server: is in a passive or standby state, meaning it does not actively participate in providing leases but monitors the active server. If the active server stops working, then the role is taken over by the standby server.
Deploying DHCP on the RRAS Server
Connect to the RRAS Server (NDL-RRAS) and navigate to the Server Manager to install the DHCP role.
Complete the post-installation DHCP configuration and authorize the DHCP Server using Domain Admin credentials.
After installation, open the DHCP Management Console
Create a new scope for our client computers.
Provide scope name.
Define the range of addresses. The scope will distribute and set the network mask. In my case, I do not want any exclusions.
IP Clients Scope (Dynamic assignment – DHCP):
- 192.168.178.220 – 192.168.178.240
Set the time how long a client can use an IP address from this scope.
Configure DHCP Options.
Define the IP Default Gateway, which is the IP address of our RRAS Server (NDL-RRAS).
The primary DNS is the IP address of the Domain Controller (192.168.178.100).
The alternate DNS is a Google DNS (8.8.8.8) for resolving external names.
Activate a scope.
Check the Scope options (current configuration) to ensure everything is in order
Check if the DHCP Server works on the client computer (NDL-CL01-MEJ).
Check the leased IPs on the DHCP server.
Configure DHCP Failover
We will also configure a hot-stand DHCP server on the domain controller.
Secondary Server [NDL-DC01]
Install the DHCP Role on the Domain Controller [NDL-DC01] as shown in the above steps. Complete the post-installation DHCP Configuration as shown in the above steps.
Primary Server [NDL-RRAS]
Configure Failover on the RRAS Server.
Create a new failover relationship.
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Test the failover configuration
Conclusion
In this blog post, we’ve taken a deep dive into the configuration of a DHCP server and its failover setup. We’ve learned how to assign static and dynamic IPs to servers and client computers respectively, and how to prepare a standby DHCP server on the Domain Controller. We’ve also explored the concept of a hot standby failover mode, ensuring that our network remains functional even if the primary DHCP server stops working.
See yaa in the next blog post! 🙂