Robtex

Up: 192.193.158.0/23
Can't show all results, try to descend to a more specific CIDR
Down left: 192.193.158.0/25
Down right: 192.193.158.128/25
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
192.193.158.11	A+PTR	smtpinbound-mpod-ru.citigroup.com
192.193.158.11	A	smtpinbound-mpod-3.citigroup.com
192.193.158.11	A	smtpinbound-mx-1.citigroup.com
192.193.158.12	A+PTR	smtpinbound-mpod-ru.citigroup.com
192.193.158.12	A	smtpinbound-mpod-3.citigroup.com
192.193.158.12	A	smtpinbound-mx-1.citigroup.com
192.193.158.13	A+PTR	smtpinbound-mpod-ru.citigroup.com
192.193.158.13	A	smtpinbound-mpod-3.citigroup.com
192.193.158.13	A	smtpinbound-mx-1.citigroup.com
192.193.158.14	A	smtpinbound-mx-1.citigroup.com
192.193.158.14	A	smtpinbound.citigroup.com
192.193.158.15	A	smtpinbound.citigroup.com
192.193.158.16	PTR	smtpoutbound.citigroup.com
192.193.158.17	PTR	smtpoutbound.citigroup.com
192.193.158.18	PTR	smtpoutbound.citigroup.com
192.193.158.69	A+PTR	smtp-edelivery-outbound.citigroup.com
192.193.158.70	A+PTR	smtp-edelivery-outbound.citigroup.com
192.193.158.71	A+PTR	smtp-edelivery-outbound.citigroup.com
192.193.158.72	A+PTR	smtp-edelivery-outbound.citigroup.com
192.193.158.73	A+PTR	smtp-edelivery-outbound.citigroup.com
192.193.158.74	A+PTR	mail-ir.citi.com
192.193.158.75	A	mail-ir.citi.com
192.193.158.76	A	mail-ir.citi.com
192.193.158.78	A+PTR	mailir.citi.com
192.193.158.79	A	2._spf.citigroup.com
192.193.158.79	A	smtpoutbound.citigroup.com
192.193.158.80	A+PTR	mailir.citi.com
192.193.158.81	A+PTR	2._spf.citigroup.com
192.193.158.81	A	smtpoutbound.citigroup.com
192.193.158.84	A+PTR	mailir.citi.com