Robtex

Up: 121.33.0.0/19
Can't show all results, try to descend to a more specific CIDR
Down left: 121.33.16.0/21
Down right: 121.33.24.0/21

IP	Type	Hostname
121.33.16.50	PTR	50.16.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.16.65	PTR	65.16.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.16.80	PTR	80.16.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.16.112	A	mail.qz5288.com
121.33.16.144	PTR	144.16.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.16.147	PTR	147.16.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.16.193	PTR	193.16.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.16.210	PTR	210.16.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.16.225	PTR	225.16.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.16.240	PTR	240.16.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.17.1	PTR	1.17.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.17.35	PTR	35.17.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.17.147	PTR	147.17.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.18.17	PTR	17.18.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.18.65	PTR	65.18.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.18.81	PTR	81.18.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.18.114	PTR	114.18.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.18.163	PTR	163.18.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.18.227	PTR	227.18.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.18.243	PTR	243.18.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.21.0	PTR	0.21.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.21.99	PTR	99.21.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.21.106	A	mail.bodayiliao.com
121.33.21.130	PTR	130.21.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.21.160	PTR	160.21.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.21.161	PTR	161.21.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.21.162	PTR	162.21.33.121.broad.gz.gd.dynamic.163data.com.cn
121.33.21.227	PTR	227.21.33.121.broad.gz.gd.dynamic.163data.com.cn