It appears Microsoft may have dropped DHCP Failover from the Windows 2008 R2 release. Hopefully they come to their senses, but we’ll see. Feel free to continue reading to see what might have been.
About time, Windows 2008 R2 will now support DHCP Failover.
DHCP server services are used to provide automated IP configuration for network endpoints. Traditionally DHCP lease information is stored in a single database, and this single computer is prone to be a single point of failure. Now you can Cluster the DHCP service, but this still leaves you venerable if the DHCP database gets corrupted. In the past the only way to elevate this was to use something like a split of the DHCP Scope between 2 servers. This did improve the reliability, but this option didn’t fit in many environments do to the need to have many extra addresses in every subnet.
In Windows Server 2008 R2, the DHCP Failover feature has been included to allieviate outages due to single server failure. The DHCP Failover feature is an implementation of the DHCP Failover protocol.
With DHCP Failover, the servers providing DHCP Server services synchronize DHCP lease information between each other. One computer is designated as the primary DHCP server and the other as the secondary DHCP server.
When computers request IP configuration, the primary DHCP server will respond. In the event that the primary DHCP server is unavailable, the secondary DHCP server will service the request. The big difference here is the secondary server knows about the current leases that the primary server made, and will be able to renew existing leases, and not be forced to give out a new address. This also eases administration and the DHCP scopes do not need to be split between servers. The DHCP Failover feature will also support two-way syncing to support load-balancing between the primary and secondary DHCP servers.
Now granted there have been some appliances in the market that supported this functionality for the past few years, but this is a great addition to the Window Server feature set. This was something that was lacking from the original Windows 2008 release, but appears to be making it in the R2.