Robtex

Up: 121.243.80.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 121.243.80.0/23
Down right: 121.243.82.0/23

IP	Type	Hostname
121.243.80.63	PTR	121.243.80.63.static-chennai.vsnl.net.in
121.243.80.249	PTR	121.243.80.249.static-chennai.vsnl.net.in
121.243.81.17	PTR	121.243.81.17.static-chennai.vsnl.net.in
121.243.81.22	PTR	121.243.81.22.static-chennai.vsnl.net.in
121.243.81.26	PTR	121.243.81.26.static-chennai.vsnl.net.in
121.243.81.125	PTR	121.243.81.125.static-chennai.vsnl.net.in
121.243.81.129	PTR	121.243.81.129.static-chennai.vsnl.net.in
121.243.81.132	PTR	121.243.81.132.static-chennai.vsnl.net.in
121.243.81.184	PTR	121.243.81.184.static-chennai.vsnl.net.in