iias.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/iias.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 7939 · primary arachne.leidenuniv.nl

Found

Primary (MNAME)

arachne.leidenuniv.nl

Contact (RNAME)

postmaster.leidenuniv.nl

Serial

7939

Refresh / retry

10800 s / 1080 s

Expire

2592000 s

Negative TTL

7200 s

Serial per nameserver

Checks

• ✓ Serial 7939 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.
• ✓ Counter serial #26

  The serial 7939 is a plain counter.

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 27406 (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 09:47 UTC and expires at 2026-10-26 10:47 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, 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