Hello again, Hari!
Unless you're using DHCP for other purposes inside your company, there's no need for DHCP services to be active to interact with Infoblox using the plug-in in this case. Making a reservation on IPAM does not require DHCP service to be.
You can combine items 2 and 4 in a single action. It is also important that you do the reservation before setting the IP on the interface or someone can take the IP before your provisioning tasks have time to fix it on the interface and do the registraton on Infoblox, leading you to duplicate IP addresses on the network.
Quick note: IPAM Reservations differ from Fixed Addresses and do not require the MAC Address to be configured. Once you're not using you're not using DHCP, the MAC Address in the reservation will be used only for registration and (maybe CMDB?) purposes.
Quick note 2: Please note that vRealize Automation (in newer versions) can use Infoblox as an endpoint for IPAM. I have not tested this new functionality yet, but it must simplify this task. I suggest you to take a time to explore it and share your experiences.
Best regards!
Paulo
