deltares.nl

ns1.deltares.nl, ns2.deltares.nl

Found

Parent zone

nl

Delegation from

ns1.dns.nl (194.0.28.53)

NS at the parent

ns1.deltares.nl, ns2.deltares.nl

NS in the zone

ns1.deltares.nl, ns2.deltares.nl

Checks

• i

  2 nameservers

  Two nameservers meet the minimum; RFC 2182 recommends three or more for important zones: ns1.deltares.nl, ns2.deltares.nl.

  #6
• ✓ Parent and zone agree #7

  The parent delegation and the zone's NS records list the same nameservers.
• ✓ Glue present and correct #8

  Glue is published for the nameservers inside the zone: ns1.deltares.nl, ns2.deltares.nl.
• ✓ All names resolve #9

  Every nameserver name has an address and is not an alias.
• !

  Nameservers in one network

  all IPv4 addresses are in 136.231.2.0/24. A single network failure takes all nameservers down; RFC 2182 recommends topologically separate networks (anycast setups are an exception).

  #10
• i

  All nameservers in one AS

  All nameserver addresses are announced by one network operator (AS1103 (SURFNET-NL - SURF B.V., NL): 2 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
• !

  No IPv6

  None of the nameservers has an IPv6 address, so IPv6-only resolvers can't reach them.

  #13

serial 2026101651 · primary ns1.deltares.nl

Found

Primary (MNAME)

ns1.deltares.nl

Contact (RNAME)

hostmaster.deltares.nl

Serial

2026101651

Refresh / retry

21600 s / 3600 s

Expire

1836900 s

Negative TTL

3600 s

Serial per nameserver

Checks

• !

  Serials differ

  The nameservers serve different versions of the zone: 2026101403 on ns2.deltares.nl (136.231.2.117); 2026101651 on ns1.deltares.nl (136.231.2.116). This is normal for a few minutes after a change; if it lasts, zone transfers to the secondaries are failing.

  #22
• ✓ Timers within recommendations #23

  SOA refresh 6h, retry 1h, expire 30615m, negative TTL 1h.
• ✓ Primary is a public nameserver #24

  The primary nameserver ns1.deltares.nl is one of the listed nameservers.
• ✓ Contact hostmaster@deltares.nl #25

  The SOA RNAME hostmaster.deltares.nl means hostmaster@deltares.nl.
• ✓ Date-based serial #26

  The serial 2026101651 follows the YYYYMMDDnn convention (2026-10-16).

Signed, DS published at parent

Found

Validated by resolver

yes

Denial of existence

NSEC

Signatures valid until

13 November 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 750 (SHA256), key tag 26402 (SHA256).
• !

  Deprecated algorithm

  SHA-1 based algorithms are deprecated and rejected by some validators: RSASHA1-NSEC3-SHA1 (7). Roll over to ECDSAP256SHA256 (13).

  #29
• ✓ Signatures valid until 2026-11-13 #30

  The earliest DNSKEY/SOA signature expires at 2026-11-13 03:57 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