Hello, smashytech
You seem to have an architecture issue rather than a DHCP configuration problem.
The configuration you're trying to reach (high available DHCP service) is achievable by using:
2 Members in a HA Pair
2 Members in a DHCP Failover Association
In the first case, if you create an HA Pair using two appliances, you can assign a range to this HA Pair and the IP lease will be made by the active node of this HA pair. If the active node fails for some reason, the passive pair will automatically be placed online (as active) will little or no impact to your dhcp clients.
From the other hand, if you use DHCP Failover association, you will have a highly available, "active-active" DHCP infrasctructure, with two appliances servicing IP addresses (and sharing the same DHCP range, with mechanisms to control the leasing of IP addresses in case of failure).
Please note that you do not need to have two different appliances (two different and separate Infoblox Grids) to "share a DHCP range". You really do not need to use backup files restored in other appliances to do this and this configuration will lead you to several issues as duplicated IP address, lack of control on your IPAM, will make everything harder to manage and you will lose all benefits that Infoblox Grid can deliver. I highly suggest you to take a look at these two mechanisms and how do you configure DHCP using then. NIOS documentation (admin guide) has several architecture examples that you can use as reference.
I also recommend you to take a time to understand how grid services work (database replication, configuration inheritance, etc). This information are also available in NIOS Admin Guide.
At training area have some on-demand classes with the basic you need to now before get in depth on Infoblox. Take a look: https://www.infoblox.com/support/training/infoblox-fundamentals/
Hope this helps!
Paulo
