hortusleiden.nl

.nl country-code

Found

TLD

.nl (country-code)

ICANN policies apply

no

Checks

• i

  .nl is a country-code TLD (ccTLD)

  Country-code TLD: governed by its local registry under national policy, not by an ICANN contract. Registrar accreditation, dispute resolution and RDAP/WHOIS rules are set by the registry.

  #1
• ✓ TLD delegated and signed #2

  .nl is delegated in the root zone and DNSSEC-signed.
• i

  Could not be checked

  The RDAP lookup failed, so this could not be checked: https://rdap.sidn.nl/domain/hortusleiden.nl returned HTTP 429

  #3

ns1.surfnet.nl, ns2.surfnet.nl, ns3.surfnet.nl

Found

Parent zone

nl

Delegation from

ns1.dns.nl (194.0.28.53)

NS at the parent

ns1.surfnet.nl, ns2.surfnet.nl, ns3.surfnet.nl

NS in the zone

ns1.surfnet.nl, ns2.surfnet.nl, ns3.surfnet.nl

Checks

• ✓ 3 nameservers #6

  Delegated to ns1.surfnet.nl, ns2.surfnet.nl, ns3.surfnet.nl.
• ✓ Parent and zone agree #7

  The parent delegation and the zone's NS records list the same nameservers.
• ✓ No glue needed #8

  All nameservers are outside the zone, so no glue records are needed.
• ✓ All names resolve #9

  Every nameserver name has an address and is not an alias.
• ✓ Nameservers in different networks #10

  The nameservers are spread over 3 IPv4 /24s and 3 IPv6 /48s.
• i

  All nameservers in one AS

  All nameserver addresses are announced by one network operator (AS1103 (SURFNET-NL - SURF B.V., NL): 6 addresses). An outage or attack on that network affects all nameservers; large anycast providers mitigate this, but a secondary DNS provider adds independence.

  #11
• i

  All nameserver names under .nl

  All nameserver names are under one TLD, so a problem with that TLD also makes the nameservers unreachable. Some operators use names under two TLDs for extra resilience.

  #12
• ✓ All reachable over IPv6 #13

  Every nameserver has an IPv6 address.

6 of 6 addresses answer authoritatively

Found

Checks

• ✓ All respond #14

  All 6 nameserver addresses answered.
• ✓ All authoritative #15

  Every responding nameserver answers authoritatively for the zone.
• ✓ No recursion #16

  The nameservers do not answer recursive queries for other domains.
• i

  Identifying string disclosed

  These nameservers answer version queries with a string that is not a version number: ns1.surfnet.nl: "This is a SURFnet nameserver - dns-beheer@surfnet.nl"; ns2.surfnet.nl: "This is a SURFnet nameserver - dns-beheer@surfnet.nl"; ns3.surfnet.nl: "This is a SURFnet nameserver - dns-beheer@surfnet.nl".

  #17
• ✓ Zone transfers refused #18

  No nameserver allows a zone transfer to the public.
• ✓ TCP supported #19

  All nameservers answer over TCP.
• ✓ EDNS supported #20

  All nameservers support EDNS(0).
• ✓ Public addresses #21

  All nameserver addresses are publicly routable.

serial 2005119616 · primary arachne.leidenuniv.nl

Found

Primary (MNAME)

arachne.leidenuniv.nl

Contact (RNAME)

postmaster.leidenuniv.nl

Serial

2005119616

Refresh / retry

10800 s / 1080 s

Expire

2592000 s

Negative TTL

7200 s

Serial per nameserver

Checks

• ✓ Serial 2005119616 everywhere #22

  All nameservers serve the same version of the zone.
• ✓ Timers within recommendations #23

  SOA refresh 3h, retry 18m, expire 30d, negative TTL 2h.
• i

  Hidden master

  The primary nameserver arachne.leidenuniv.nl is not listed as a nameserver: a hidden master that only feeds the public secondaries. That is a common setup; make sure it is not reachable for zone transfers from outside.

  #24
• ✓ Contact postmaster@leidenuniv.nl #25

  The SOA RNAME postmaster.leidenuniv.nl means postmaster@leidenuniv.nl.
• ✓ Timestamp serial #26

  The serial 2005119616 is a Unix timestamp (2033-07-16 09:40 UTC).

Signed, DS published at parent

Found

Validated by resolver

yes

Denial of existence

NSEC

Signatures valid until

26 October 2026

DS at the parent

DNSKEY in the zone

Checks

• ✓ Signed and validated #27

  The zone is signed, the parent publishes a DS record, and the resolver validates the answers.
• ✓ DS matches a key #28

  The DS record at the parent matches a key in the zone: key tag 2545 (SHA256).
• ✓ Modern algorithms #29

  Key algorithms: RSASHA256 (8).
• ✓ Short-lived signatures (online signing) #30

  Signatures are valid for 97h0m0s and created on demand; the current one was made at 2026-10-22 09:03 UTC and expires at 2026-10-26 09:38 UTC.
• i

  NSEC

  The zone uses NSEC, so its full contents can be listed by walking the NSEC chain. That is fine unless the names are sensitive.

  #31

10 records at the apex

Found

Read from

192.87.106.101:53

Checks

• ✓ TTLs within range #32

  TTLs: A 8h, AAAA 5m, MX 8h, NS 8h. The NS TTL at the parent is 1h and in the zone 8h; resolvers may use either.
• ✓ No CNAME at the apex #33

  The zone apex has no CNAME record.
• ✓ No wildcard #34

  Names that don't exist return NXDOMAIN.
• i

  No CAA records

  Without CAA records any certificate authority may issue certificates for this domain. A CAA record limits issuance to the CAs you use.

  #35