Modern IPAM tools integrate with DNS and DHCP. When you assign an IP, the tool creates the DNS record and DHCP reservation automatically.
Popular solutions: NetBox (open source, API-driven), phpIPAM (free, good for smaller networks), Infoblox (enterprise-grade, expensive), and SolarWinds IPAM.
Features that matter: subnet calculator and planning tools, DHCP and DNS integration, API for automation, audit logging, and scanning to discover existing assignments.
I recommend NetBox for most teams. It's free, well-documented, and has an API for automation.