Robtex

Up: 173.20.48.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 173.20.52.0/23
Down right: 173.20.54.0/23

IP	Type	Hostname
173.20.52.33	PTR	173-20-52-33.client.mchsi.com
173.20.52.90	A	173-20-52-90.client.mchsi.com
173.20.52.199	A+PTR	173-20-52-199.client.mchsi.com
173.20.55.160	A+PTR	173-20-55-160.client.mchsi.com
173.20.55.181	A+PTR	173-20-55-181.client.mchsi.com