2001:8d8:100f:f000::252

Reverse address entry: 2.5.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.f.f.0.0.1.8.d.8.0.1.0.0.2.ip6.arpa

2001:8d8:100f:f000::252 has no DNS entries .

Explore by label: 2 . 5 . 2 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . f . f . 0 . 0 . 1 . 8 . d . 8 . 0 . 1 . 0 . 0 . 2 . ip6 . arpa

RIPE6 2.5.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.f.f.0.0.1.8.d.8.0.1.0.0.2.ip6.arpa
PTR2001-08d8-100f-f000-0000-0000-0000-0252.elastic-ssl.ui-r.com expired since 3 days, 13 hours
Show 1 expired records

This top-level domain has no publically available whois server. Try going to www.nic.arpa.