Robtex

Up: 72.128.192.0/18
Can't show all results, try to descend to a more specific CIDR
Down left: 72.128.224.0/20
Down right: 72.128.240.0/20

IP	Type	Hostname
72.128.238.32	PTR	mta-72-128-238-32.wi.rr.com
72.128.238.66	PTR	mta-72-128-238-66.wi.rr.com
72.128.238.98	PTR	mta-72-128-238-98.wi.rr.com
72.128.238.129	PTR	mta-72-128-238-129.wi.rr.com
72.128.238.194	PTR	mta-72-128-238-194.wi.rr.com
72.128.238.225	PTR	mta-72-128-238-225.wi.rr.com
72.128.248.1	PTR	mta-72-128-248-1.wi.rr.com