Robtex

Up: 72.21.22.0/23
Can't show all results, try to descend to a more specific CIDR
Down left: 72.21.23.0/25
Down right: 72.21.23.128/25
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
72.21.23.21	A	ts.techhero.us
72.21.23.22	PTR	mail.techhero.com
72.21.23.22	PTR	mail.techhero.us
72.21.23.64	A	mail.mydatahero.com
72.21.23.64	A	mail.techlogic.biz
72.21.23.80	PTR	ns1.kosmos.net
72.21.23.80	A	ns.kosmos.net
72.21.23.82	PTR	ns2.kosmos.net
72.21.23.100	PTR	wilsongarber.com
72.21.23.100	PTR	apply.techhero.com
72.21.23.100	PTR	intranet.techhero.com
72.21.23.110	A	spamgate1.blueskyonline.net
72.21.23.140	A+PTR	hdd.clsmf.org
72.21.23.140	PTR	mail.clsmf.org
72.21.23.177	A	mail.esfl.us
72.21.23.192	A	mail.esfl.us
72.21.23.198	A	mail.clsmf.org
72.21.23.199	PTR	autodiscover.clsmf.org
72.21.23.199	PTR	exch04.clsmf.org
72.21.23.199	A+PTR	mail.clsmf.org
72.21.23.200	A+PTR	exch02.clsmf.org
72.21.23.204	A	vts5.clsmf.org
72.21.23.205	A	vts3.clsmf.org
72.21.23.206	A	tsls.clsmf.org
72.21.23.210	A	vts1.clsmf.org
72.21.23.241	A	enviworld.com
72.21.23.242	A	faithxt.com