Robtex

Up: 192.72.136.0/24
Can't show all results, try to descend to a more specific CIDR
Down left: 192.72.136.0/26
Down right: 192.72.136.64/26
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
192.72.136.1	A	maila.opto.com.tw
192.72.136.4	A+PTR	spama.opto.com.tw
192.72.136.4	A	mx1.opto.com.tw
192.72.136.4	A	spam.opto.com.tw
192.72.136.7	PTR	proxya.opto.com.tw
192.72.136.7	A	www.opto.com.tw
192.72.136.7	A	opto.com.cn