There's a difference in the TTL of glue records returned in a priming query from different root servers. There's nothing wrong with a nameserver lowering the TTL in a response [RFC2181], but it's an observable difference in behavior. Perhaps some DNS implementation is clamping the glue to TTLs of the NS records. Both TTLs are observed on multiple root server letters respectively. [muks@jurassic ~]$ dig +nord +short @l.root-servers.net root-servers.net soa a.root-servers.net. nstld.verisign-grs.com. 2020060800 14400 7200 1209600 3600000 [muks@jurassic ~]$ dig +nord @l.root-servers.net . ns ; <<>> DiG 1.1.1.20200608151533.e8a2352e96 <<>> +nord @l.root-servers.net . ns ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26630 ;; flags: qr aa; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 27 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;. IN NS ;; ANSWER SECTION: . 518400 IN NS a.root-servers.net. . 518400 IN NS b.root-servers.net. . 518400 IN NS c.root-servers.net. . 518400 IN NS d.root-servers.net. . 518400 IN NS e.root-servers.net. . 518400 IN NS f.root-servers.net. . 518400 IN NS g.root-servers.net. . 518400 IN NS h.root-servers.net. . 518400 IN NS i.root-servers.net. . 518400 IN NS j.root-servers.net. . 518400 IN NS k.root-servers.net. . 518400 IN NS l.root-servers.net. . 518400 IN NS m.root-servers.net. ;; ADDITIONAL SECTION: a.root-servers.net. 518400 IN A 198.41.0.4 b.root-servers.net. 518400 IN A 199.9.14.201 c.root-servers.net. 518400 IN A 192.33.4.12 d.root-servers.net. 518400 IN A 199.7.91.13 e.root-servers.net. 518400 IN A 192.203.230.10 f.root-servers.net. 518400 IN A 192.5.5.241 g.root-servers.net. 518400 IN A 192.112.36.4 h.root-servers.net. 518400 IN A 198.97.190.53 i.root-servers.net. 518400 IN A 192.36.148.17 j.root-servers.net. 518400 IN A 192.58.128.30 k.root-servers.net. 518400 IN A 193.0.14.129 l.root-servers.net. 518400 IN A 199.7.83.42 m.root-servers.net. 518400 IN A 202.12.27.33 a.root-servers.net. 518400 IN AAAA 2001:503:ba3e::2:30 b.root-servers.net. 518400 IN AAAA 2001:500:200::b c.root-servers.net. 518400 IN AAAA 2001:500:2::c d.root-servers.net. 518400 IN AAAA 2001:500:2d::d e.root-servers.net. 518400 IN AAAA 2001:500:a8::e f.root-servers.net. 518400 IN AAAA 2001:500:2f::f g.root-servers.net. 518400 IN AAAA 2001:500:12::d0d h.root-servers.net. 518400 IN AAAA 2001:500:1::53 i.root-servers.net. 518400 IN AAAA 2001:7fe::53 j.root-servers.net. 518400 IN AAAA 2001:503:c27::2:30 k.root-servers.net. 518400 IN AAAA 2001:7fd::1 l.root-servers.net. 518400 IN AAAA 2001:500:9f::42 m.root-servers.net. 518400 IN AAAA 2001:dc3::35 ;; Query time: 33 msec ;; SERVER: 199.7.83.42#53(199.7.83.42) ;; WHEN: Fri Jun 19 03:52:09 IST 2020 ;; MSG SIZE rcvd: 811 [muks@jurassic ~]$ dig +nord +short @m.root-servers.net root-servers.net soa a.root-servers.net. nstld.verisign-grs.com. 2020060800 14400 7200 1209600 3600000 [muks@jurassic ~]$ dig +nord @m.root-servers.net . ns ; <<>> DiG 1.1.1.20200608151533.e8a2352e96 <<>> +nord @m.root-servers.net . ns ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45391 ;; flags: qr aa; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 27 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;. IN NS ;; ANSWER SECTION: . 518400 IN NS d.root-servers.net. . 518400 IN NS g.root-servers.net. . 518400 IN NS i.root-servers.net. . 518400 IN NS l.root-servers.net. . 518400 IN NS j.root-servers.net. . 518400 IN NS f.root-servers.net. . 518400 IN NS c.root-servers.net. . 518400 IN NS b.root-servers.net. . 518400 IN NS m.root-servers.net. . 518400 IN NS a.root-servers.net. . 518400 IN NS e.root-servers.net. . 518400 IN NS k.root-servers.net. . 518400 IN NS h.root-servers.net. ;; ADDITIONAL SECTION: a.root-servers.net. 3600000 IN A 198.41.0.4 b.root-servers.net. 3600000 IN A 199.9.14.201 c.root-servers.net. 3600000 IN A 192.33.4.12 d.root-servers.net. 3600000 IN A 199.7.91.13 e.root-servers.net. 3600000 IN A 192.203.230.10 f.root-servers.net. 3600000 IN A 192.5.5.241 g.root-servers.net. 3600000 IN A 192.112.36.4 h.root-servers.net. 3600000 IN A 198.97.190.53 i.root-servers.net. 3600000 IN A 192.36.148.17 j.root-servers.net. 3600000 IN A 192.58.128.30 k.root-servers.net. 3600000 IN A 193.0.14.129 l.root-servers.net. 3600000 IN A 199.7.83.42 m.root-servers.net. 3600000 IN A 202.12.27.33 a.root-servers.net. 3600000 IN AAAA 2001:503:ba3e::2:30 b.root-servers.net. 3600000 IN AAAA 2001:500:200::b c.root-servers.net. 3600000 IN AAAA 2001:500:2::c d.root-servers.net. 3600000 IN AAAA 2001:500:2d::d e.root-servers.net. 3600000 IN AAAA 2001:500:a8::e f.root-servers.net. 3600000 IN AAAA 2001:500:2f::f g.root-servers.net. 3600000 IN AAAA 2001:500:12::d0d h.root-servers.net. 3600000 IN AAAA 2001:500:1::53 i.root-servers.net. 3600000 IN AAAA 2001:7fe::53 j.root-servers.net. 3600000 IN AAAA 2001:503:c27::2:30 k.root-servers.net. 3600000 IN AAAA 2001:7fd::1 l.root-servers.net. 3600000 IN AAAA 2001:500:9f::42 m.root-servers.net. 3600000 IN AAAA 2001:dc3::35 ;; Query time: 104 msec ;; SERVER: 202.12.27.33#53(202.12.27.33) ;; WHEN: Fri Jun 19 03:51:46 IST 2020 ;; MSG SIZE rcvd: 811 [muks@jurassic ~]$ Mukund