Robtex

Up: 72.21.32.0/20
Can't show all results, try to descend to a more specific CIDR
Down left: 72.21.32.0/22
Down right: 72.21.36.0/22
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
72.21.32.1	PTR	1.32.21.72.static.reverse.ltdomains.com
72.21.32.83	PTR	nsa1.nuspace.net
72.21.32.122	A	weightlossdiscussionforum.com
72.21.32.122	A	gunbrokerforum.com
72.21.32.178	A	mail.mohammedkhanandsonsjewellers.com
72.21.33.187	A	ns2.flowerhornusa.com
72.21.33.227	PTR	service.sourcehosting.org
72.21.33.248	A	bestidsonline.net
72.21.33.248	A	easyworkace.net
72.21.33.248	A	heatingace.net
72.21.34.82	PTR	ws04.hexium.com.ar
72.21.34.98	A	largeid.net
72.21.34.98	A	straightace.net
72.21.34.98	A	aceinformation.net
72.21.34.105	PTR	105.34.21.72.static.reverse.ltdomains.com
72.21.34.105	A	largepassword.net
72.21.34.105	A	www.qualityace.net
72.21.34.166	A	mail.onlinekharid.com
72.21.34.166	A	www.onlinekharid.ir
72.21.34.188	A	mail.nitrohaulics.com
72.21.34.235	A	someonebigger.net
72.21.34.235	A	seasidesaver.net
72.21.34.235	A	smallids.net
72.21.35.70	A	indomitus.biz
72.21.35.98	PTR	writely.com
72.21.36.122	A	thomasdelivers.com
72.21.36.122	A	s1.plasticgames.com
72.21.36.234	PTR	234.36.21.72.static.reverse.ltdomains.com
72.21.37.2	A	lnxbrz3104.cust.fluidata.com
72.21.37.65	PTR	65.37.21.72.static.reverse.ltdomains.com
72.21.37.66	PTR	66.37.21.72.static.reverse.ltdomains.com
72.21.37.98	A	web.cpammali.net
72.21.37.98	A	ns1.woolywoods.us
72.21.37.98	A	www.cpammali.net
72.21.37.101	A	icims-talentplatform-37101.email.icims.tools
72.21.37.115	A+PTR	icims-talentplatform-37115.email.icims.tools
72.21.37.136	A	sf-capeunionmart.mobi
72.21.37.138	PTR	138.37.21.72.static.reverse.ltdomains.com
72.21.37.138	A	celebritybattles.com
72.21.37.138	A	celebritypapers.com
72.21.37.161	A	sfkiko.mobi
72.21.38.130	A	plug.wire.org.za
72.21.38.138	PTR	138.38.21.72.static.reverse.ltdomains.com
72.21.38.157	A	mail.karapuz.com.ua
72.21.38.157	A	*.karapuz.com.ua
72.21.38.157	A	karapuz.com.ua
72.21.39.122	A	mail.gdreducation.com
72.21.39.123	PTR	123.39.21.72.static.reverse.ltdomains.com
72.21.39.123	A	frsmtpa.verinthms.com
72.21.39.179	PTR	179.39.21.72.static.reverse.ltdomains.com
72.21.39.187	A	ns2.warmhat.com
72.21.39.194	A	ns1.host-tech.net
72.21.39.219	A	ns2.luminousstudio.com