Robtex

Up: 188.172.138.0/23
Can't show all results, try to descend to a more specific CIDR
Down left: 188.172.138.0/25
Down right: 188.172.138.128/25
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
188.172.138.1	PTR	outbyoip1.pod18.euc1.zdsys.com
188.172.138.1	A	bootstrappedventures.zendesk.com
188.172.138.1	A	bridgeclublive.zendesk.com
188.172.138.2	A	outbyoip2.pod18.euc1.zdsys.com
188.172.138.3	PTR	188-172-138-3.ctelnetco.com
188.172.138.3	A	pubsub-shard1-7-2.zendesk.com
188.172.138.3	A	pubsub-shard1-7-1.zendesk.com
188.172.138.4	A	outbyoip4.pod18.euc1.zdsys.com
188.172.138.5	A	outbyoip5.pod18.euc1.zdsys.com
188.172.138.6	A	outbyoip6.pod18.euc1.zdsys.com
188.172.138.7	A	outbyoip7.pod18.euc1.zdsys.com
188.172.138.8	A	outbyoip8.pod18.euc1.zdsys.com
188.172.138.9	PTR	188-172-138-9.ctelnetco.com
188.172.138.9	A	p7.zdusercontent.com
188.172.138.9	A	zdusercontent.vip.pod7.fra1.zdsys.com
188.172.138.15	PTR	outbyoip15.pod18.euc1.zdsys.com
188.172.138.65	PTR	188-172-138-65.ctelnetco.com
188.172.138.66	PTR	188-172-138-66.ctelnetco.com
188.172.138.66	A	tradeshift.ssl.zendesk.com
188.172.138.74	PTR	188-172-138-74.ctelnetco.com
188.172.138.74	A	support.hostway.com
188.172.138.82	PTR	188-172-138-82.ctelnetco.com
188.172.138.95	A	autocom.ssl.zendesk.com
188.172.138.98	PTR	188-172-138-98.ctelnetco.com
188.172.138.98	A	strava.ssl.zendesk.com
188.172.138.98	A	support.strava.com
188.172.138.129	PTR	188-172-138-129.ctelnetco.com
188.172.138.129	A	cdkeys.ssl.zendesk.com
188.172.138.129	A	support.cdkeys.com
188.172.138.130	A	cerberusllc.ssl.zendesk.com
188.172.138.130	A	support.cerberusftp.com
188.172.138.131	PTR	188-172-138-131.ctelnetco.com
188.172.138.131	A	cloudtrax.ssl.zendesk.com
188.172.138.132	A	getcolor.ssl.zendesk.com
188.172.138.134	PTR	188-172-138-134.ctelnetco.com
188.172.138.134	A	ableton.ssl.zendesk.com
188.172.138.134	A	help.ableton.com
188.172.138.156	PTR	188-172-138-156.ctelnetco.com
188.172.138.156	A	jbsupsource.ssl.zendesk.com
188.172.138.156	A	youtrack-support.jetbrains.com