Robtex

Up: 74.6.0.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 74.6.4.0/23
Down right: 74.6.6.0/23

IP	Type	Hostname
74.6.4.4	PTR	unknown-74-6-4-x.yahoo.com
74.6.4.10	PTR	unknown-74-6-4-x.yahoo.com
74.6.4.154	PTR	su1331.usne1.dht.bf1.yahoo.com
74.6.6.7	PTR	unknown-74-6-6-x.yahoo.com
74.6.6.8	PTR	unknown-74-6-6-x.yahoo.com
74.6.6.39	PTR	unknown-74-6-6-x.yahoo.com
74.6.7.86	PTR	client9002.udb.bf1.yahoo.com
74.6.7.97	PTR	unknown-74-6-7-x.yahoo.com
74.6.7.103	PTR	unknown-74-6-7-x.yahoo.com
74.6.7.147	PTR	pud12008-stg.udb.bf1.yahoo.com
74.6.7.190	PTR	unknown-74-6-7-x.yahoo.com
74.6.7.197	PTR	unknown-74-6-7-x.yahoo.com
74.6.7.205	PTR	ge-0-16.bas5-1-con.ac2.yahoo.com
74.6.7.217	PTR	pud12028-stg.udb.bf1.yahoo.com