Robtex

Up: 170.72.16.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 170.72.20.0/23
Down right: 170.72.22.0/23
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
170.72.20.89	A+PTR	170-72-20-89.ut.vivintwireless.net
170.72.20.89	A	geoffreyblotter.me
170.72.20.98	A+PTR	170-72-20-98.ut.vivintwireless.net
170.72.20.98	A	geoffreyblotter.me
170.72.22.162	A	djdaverocks.com
170.72.22.162	A	cleanrequests.com
170.72.22.162	A	davidwariner.com
170.72.22.232	A	nateastle.no-ip.biz
170.72.23.2	A+PTR	170-72-23-2.ut.vivintwireless.net