Synchronizing DHCP Failover Relationships
DHCP failover works by replicating IP address leases and settings in 2 servers operate in a failover relationship where an active server is. Configuring the DHCP failover in your LAN is a simple operation to improve the reliability of the network. There are two main ways to provide. Server A, and Server B. I recently added DHCP services to Server B and It replicated scope and relationship data fine, and all looked good.
The other is the set of scopes that are part of the failover relation. These scopes are set up identically between the two servers when failover is configured. Once set up in this fashion, the DHCP servers replicate the IP address leases and associated client information between them and thereby have up-to-date information of all the clients on the network.
So even when one of the servers goes down — either in a planned or in an unplanned manner — the other DHCP server has the required IP address lease data to continue serving the clients.
Load Balance and Hot Standby. The Load Balance mode is essentially an Active-Active configuration wherein both DHCP servers serve client requests with a configured load distribution percentage. We will look at how the DHCP servers distribute client load in a later post. The Hot Standby mode results in an Active-Passive configuration.
You will be required to designate one of the two DHCP servers as the active server and the other as standby.
Step by Step DHCP Failover in Windows Server 2016
The standby server is dormant with regard to serving client requests as long as the active server is up. However, the standby server receives all the inbound lease updates from the active DHCP server and keeps its database up to date. The DHCP servers in a failover relationship can be in different subnets and can even be in different geographical sites. Deployment Topologies The support of these two modes enables a wide range of deployment topologies. The most rudimentary one is where two servers in a Load Balance or Hot Standby mode serve a set of subnets which are in the same site.
A slightly more involved deployment where failover is being deployed across two different sites is illustrated in Figure 1.
To ensure high availability of the DHCP service at both the sites, one can setup two failover relationships in Hot Standby mode. One can visualize a ring topology involving multiple sites where a server at each site - in addition to being the active server for the local network — is the standby server for another site. The failover relationships can be set up to form a ring topology through the DHCP servers at different sites.
Hub-and-Spoke is another multi-site deployment topology which lends itself quite well to how organizations are looking to deploy failover. These mechanisms have their own disadvantages. When the primary server fails, the hot standby server will start issuing leases.
Since failover is implemented at the scope level, you can configure a DHCP server as the primary server for one scope, and as the secondary server for another one. Which is a straightforward process in Server R2, since no configuration is made during the installation of the role.
You only need to authorize the server, after installing the DHCP server role, which is also performed in Server Manager.
Windows Server DHCP Failover replicating function performs overwrite ?
Only on one server of course. Right-click a particular scope, or right-click the IPv4 node, and select Configure Failover. Former will let you configure failover for a particular scope, while latter will let you configure failover for any or all scopes. Which is what I did. This relationship will not only pertain to the scope, but it will be created between the two servers.
Meaning even if you remove the scope from the relationship later on, the relationship itself will remain, with all of the settings you define here.
You can freely reuse this relationship between the two servers on other scopes later on. You are also free to create more than one relationship between two servers. The configuration options here are as follows; Give the failover relationship a friendly name. This time also determines how long the active server waits with its partner offline before assuming total control of the DHCP scope.
If this setting is disabled, an administrator must manually tell DHCP Failover that a server is in a partner-down state.
You can only change to partner down state, if the communication has been interrupted between the two servers. If the DHCP Server service notices that the communication is in fact intact, you will not be able to change to partner down state. Enable Message Authentication Enables authentication of the failover replication traffic between partners. What this basically does is to secure communications between failover partners.
Shared Secret If you have selected the Enable Message Authentication check box, then you will need to specify a password here for authentication of traffic.