Hi @usaf_27
This is not possible. The internal DNAC IPAM library controls IP allocation during LAN automation and cannot be modified as far as I'm aware. See the following LAN automation deployment guide that details IP pool planning/allocation.
https://www.cisco.com/c/en/us/support/docs/cloud-systems-management/dna-center/215336-lan-automation-step-by-step-deployment.html
Are you using ISE for AAA RADIUS/TACACS? If so, once the devices have been discovered and onboarded into DNAC using LAN automation, DNAC will automatically add the devices to ISE and enable RADIUS/TACACS as required avoiding the need to pre-plan IP allocations and add the devices to ISE manually.
If you want to set your own loopback addresses then you will need to deploy the underlay configuration manually using a templated design. I've had to do this for a customer that wanted to retain control over IP address allocation and ISIS link metrics
Will
