Convert IPs to CIDR ranges to expand network attack surface
go get -u github.com/daehee/cidra
Download the latest ip2asn.com database to working directory:
wget https://iptoasn.com/data/ip2asn-combined.tsv.gz
Pipe in list of IP addresses resolved from target subdomains:
cat giant-list-of-ips.txt | cidra
Add resulting CIDRs to your next nmap
or masscan
run.