Robtex

Up: 213.217.40.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 213.217.40.0/23
Down right: 213.217.42.0/23
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
213.217.40.2	PTR	213.217.40.2.parsonline.net
213.217.40.74	A+PTR	relay.parsonline.net
213.217.40.74	A	relay0.parsonline.net
213.217.40.74	A	mx15.parsonline.net
213.217.40.130	PTR	213.217.40.130.parsonline.net
213.217.40.138	PTR	213.217.40.138.parsonline.net
213.217.40.142	PTR	213.217.40.142.parsonline.net
213.217.40.186	PTR	213.217.40.186.parsonline.net
213.217.40.187	PTR	213.217.40.187.parsonline.net
213.217.40.187	A	mail.parsnetworks.com
213.217.40.206	PTR	mail.exg.parsonline.net
213.217.42.116	PTR	213.217.42.116.parsonline.net
213.217.42.175	PTR	213.217.42.175.parsonline.net
213.217.42.209	PTR	mail.iomserv.com
213.217.42.211	A	mail.maadiranservice.ir
213.217.43.6	PTR	213.217.43.6.parsonline.net
213.217.43.18	PTR	213.217.43.18.parsonline.net
213.217.43.32	PTR	213.217.43.32.parsonline.net
213.217.43.43	A	mail.mapnagroup.com
213.217.43.44	A+PTR	map-smtp-gw1.mapnagroup.com
213.217.43.46	PTR	213.217.43.46.parsonline.net
213.217.43.46	A	www.mapna.info
213.217.43.46	A	mapna.net
213.217.43.107	A	refahiajoodanieh.com
213.217.43.107	A	refahiajodanieh.com
213.217.43.152	A	mail.kplusi.ir
213.217.43.182	PTR	mail.unileveriran.com