Robtex

Up: 217.163.20.0/22
Can't show all results, try to descend to a more specific CIDR
Down left: 217.163.20.0/24
Down right: 217.163.21.0/24
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
217.163.20.0	PTR	unknown-217-163-20-x.yahoo.com
217.163.20.4	A+PTR	ge-3-1-7.msr1.ch1.yahoo.com
217.163.20.7	PTR	gi-1-8.bas-b2.ch1.yahoo.com
217.163.20.18	PTR	unknown.yahoo.com
217.163.20.37	PTR	eth-1-2-p207.tun1.ch1.yahoo.com
217.163.20.37	A	tun1.ch1.yahoo.com
217.163.20.40	A	c4948-z1.ch1.yahoo.com
217.163.20.65	A+PTR	ha1.vl-308.bas-c.ch1.yahoo.com
217.163.20.131	A+PTR	vl-309.bas-c1.ch1.yahoo.com
217.163.20.195	A+PTR	vl-307b.bas-c1.ch1.yahoo.com
217.163.20.198	A+PTR	c4948-c2.ch1.yahoo.com
217.163.20.202	PTR	unknown.yahoo.com
217.163.20.202	A	c4948-c6.ch1.yahoo.com
217.163.20.211	A+PTR	c4948-c103.ch1.yahoo.com
217.163.20.220	PTR	unknown.yahoo.com
217.163.20.220	A	c4948-c23.ch1.yahoo.com
217.163.20.224	A+PTR	c4948-c27.ch1.yahoo.com
217.163.20.225	A+PTR	c4948-c28.ch1.yahoo.com
217.163.20.227	A+PTR	c4948-c30.ch1.yahoo.com
217.163.21.3	PTR	unknown.yahoo.com
217.163.21.12	PTR	si-c5.vl320.ch1.yahoo.com
217.163.21.13	A+PTR	ve10.si-c3.ch1.yahoo.com
217.163.21.31	PTR	unknown.yahoo.com
217.163.21.31	A	bg0212.rm.ch1.yahoo.com
217.163.21.34	PTR	unknown.yahoo.com
217.163.21.34	A	ad.marschannels.com
217.163.21.34	A	fd-world.ngd.ysm.yahoodns.net
217.163.21.35	PTR	mpr2.ngd.vip.ch1.yahoo.com
217.163.21.35	A	ad.marschannels.com
217.163.21.35	A	fd-world.ngd.ysm.yahoodns.net
217.163.21.36	A+PTR	mpr3.ngd.vip.ch1.yahoo.com
217.163.21.37	A+PTR	mpr4.ngd.vip.ch1.yahoo.com
217.163.21.38	PTR	unknown.yahoo.com
217.163.21.38	A	mpr5.ngd.vip.ch1.yahoo.com
217.163.21.39	A+PTR	mpr6.ngd.vip.ch1.yahoo.com
217.163.21.40	PTR	unknown-217-163-21-x.yahoo.com
217.163.21.40	A	mpr7.ngd.vip.ch1.yahoo.com
217.163.21.41	A+PTR	mpr8.ngd.vip.ch1.yahoo.com
217.163.21.71	PTR	unknown-217-163-21-x.yahoo.com
217.163.21.78	PTR	unknown.yahoo.com
217.163.21.78	A	mpr0111.rm.ch1.yahoo.com
217.163.21.121	A	mpr0140.rm.ch1.yahoo.com
217.163.21.124	PTR	mpr0143.rm.ch1.yahoo.com
217.163.21.144	PTR	mpr0159.rm.ch1.yahoo.com
217.163.21.160	A+PTR	tpi0103.rm.ch1.yahoo.com
217.163.21.168	A	cms0001.rm.ch1.yahoo.com
217.163.21.181	A	tpi0116.rm.ch1.yahoo.com
217.163.21.206	A+PTR	tpi0132.rm.ch1.yahoo.com
217.163.21.211	PTR	unknown.yahoo.com
217.163.21.211	A	tpi0137.rm.ch1.yahoo.com
217.163.21.224	A	bap0013.rm.ch1.yahoo.com
217.163.21.255	PTR	unknown-217-163-21-x.yahoo.com