You can configure a network profile to support IP address ranges for an existing network when that network profile is used in a vRealize Automation blueprint that uses external IPAM integration.
An example is provided within the context of a vendor-specific sample workflow at Configure a network and network profile to use external IPAM for an existing network in vRealize Automation. The overall vendor-specific workflow for external IPAM integration is at Tutorial: Configuring VMware Cloud on AWS for vRealize Automation.
For related information, see How do I configure a network profile to support an on-demand network for an external IPAM integration in vRealize Automation.