Basic NIOS can do basic Network Discover:

Data Management > IPAM > Select network and click “Discovery”. IPv4 only and uses NMAP.

The NetworkInsight license (a.k.a Discovery license) allows the Infoblox to use SNMP and other protocols to discover and catalogue a diverse assortment of device types including routers, enterprise switches, firewalls and security appliance, load balancer, enterprise printer, wireless access points, end hosts, application servers, etc.

So, NetworkInsight provides better data. However, as with the built in discovery functionality, you need to be careful. Depending on how and where it is being used in the network, it may be advisable to deploy more appliances (e.g. one in America, one in EMEA, one in APAC, etc) to reduce the amount of probing traffic flowing around the globe.

WHen deploying multiple devices, you use NIOS devices for probing the networks (we call them probes) and they report to the “consolidator” devices which then report to the Grid Master. Technically it can happen on the Grid Master (or preferably the Grid Master Candidate) but that can cause messness with the firewall rules.

A NetworkInsight appliance can be standalone. It can't do DNS or DHCP but it can gather IPAM data just like a “normal” NIOS Grid.

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From the Docs

When the Grid Master database reaches its maximum capacity (the maximum capacity varies based on the appliance model), the Grid Master stops updating the database and requests that the Grid member stop the discovery. When the discovering Grid member database reaches its capacity, the Grid member pauses the discovery.

To convert multiple networks from unmanaged to managed, under IPAM, add filter for managed=no and then export to IB CSV format. Use CSV Import to delete them. Then use same file to add them back, and they will be managed.

A discovered entity is considered “unmanaged” if it is discovered in a network for which no information is being stored in the NIOS database. You are not able to configure unmanaged objects in NIOS. Depending on the nature of the discovered entity, you may convert certain unmanaged entities into managed objects so you can manage them through Grid Manager. When an entity is in the managed state, you can configure settings such as applying permissions to it, limiting who can modify the configurations and deployments, and when those changes can be applied. You cannot do so with unmanaged objects.