Robtex

Up: 203.152.48.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 203.152.48.0/23
Down right: 203.152.50.0/23
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
203.152.50.34	PTR	mail.group-ifa.com
203.152.50.34	PTR	mail.meikithai.com
203.152.50.34	PTR	mail.stc-com.com
203.152.50.130	A+PTR	mail.alphacompanies.com
203.152.50.132	A+PTR	mail1.alphacompanies.com
203.152.50.203	PTR	smtp.uobkayhian.co.th
203.152.50.230	PTR	mail.multimedia.co.th