duo.nl

Checked 21 October 2026, 21:15 UTC · via 8.8.8.8
!Passed with warnings
30 passed 1 warning 0 failed 4 info

Registration

info

.nl country-code · Rijksoverheid

Found

TLD
.nl (country-code)
ICANN policies apply
no
Registrar
Rijksoverheid
Registered
18 December 1998
Last changed
1 June 2026
Status
active
Registry nameservers
ns1.surfnet.nl, ns1.zurich.surf.net, ns2.surfnet.nl, ns3.surfnet.nl
RDAP server
https://rdap.sidn.nl/

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
    Expiry date not published
    The registry does not publish the expiry date in RDAP. Check it with your registrar.
    #3
  • i
    No transfer lock
    The domain has no transfer lock (status: active). A registrar lock protects against unauthorized transfers.
    #4
  • ✓ Registry and delegation match #5
    The nameservers registered at the registry are the ones published in DNS.

Delegation

pass

ns1.surfnet.nl, ns1.zurich.surf.net, 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, ns1.zurich.surf.net, ns2.surfnet.nl, ns3.surfnet.nl
NS in the zone
ns1.surfnet.nl, ns1.zurich.surf.net, ns2.surfnet.nl, ns3.surfnet.nl
NameserverAddressesNetwork (AS)Glue
ns1.surfnet.nl192.87.106.101 2001:610:1:800a:192:87:106:101AS1103 SURFNET-NL - SURF B.V., NL AS1103 SURFNET-NL - SURF B.V., NL192.87.106.101 2001:610:1:800a:192:87:106:101
ns1.zurich.surf.net195.176.255.9 2001:620:0:9::1103AS559 Switch - SWITCH, CH AS559 Switch - SWITCH, CH-
ns2.surfnet.nl192.87.36.2 2001:610:3:200a:192:87:36:2AS1103 SURFNET-NL - SURF B.V., NL AS1103 SURFNET-NL - SURF B.V., NL192.87.36.2 2001:610:3:200a:192:87:36:2
ns3.surfnet.nl195.169.124.71 2001:610:0:800c:195:169:124:71AS1103 SURFNET-NL - SURF B.V., NL AS1103 SURFNET-NL - SURF B.V., NL195.169.124.71 2001:610:0:800c:195:169:124:71

Checks

  • ✓ 4 nameservers #6
    Delegated to ns1.surfnet.nl, ns1.zurich.surf.net, 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 4 IPv4 /24s and 4 IPv6 /48s.
  • ✓ 2 autonomous systems #11
    The nameservers are spread over: AS1103 (SURFNET-NL - SURF B.V., NL): 6 addresses; AS559 (Switch - SWITCH, CH): 2 addresses.
  • ✓ Nameserver names under 2 TLDs #12
    Nameserver names use the TLDs .net, .nl.
  • ✓ All reachable over IPv6 #13
    Every nameserver has an IPv6 address.

Nameservers

info

8 of 8 addresses answer authoritatively

Found

NameserverAnswerRecursionTCP / EDNSAXFRVersion
ns1.surfnet.nl 192.87.106.101NOERROR, 14 ms, authoritativenoyes / yesrefusedThis is a SURFnet nameserver - dns-beheer@surfnet.nl
ns1.surfnet.nl 2001:610:1:800a:192:87:106:101NOERROR, 14 ms, authoritativenoyes / yesrefusedThis is a SURFnet nameserver - dns-beheer@surfnet.nl
ns1.zurich.surf.net 195.176.255.9NOERROR, 9 ms, authoritativenoyes / yesrefusedThis is a SURFnet nameserver - dns-beheer@surf.nl
ns1.zurich.surf.net 2001:620:0:9::1103NOERROR, 10 ms, authoritativenoyes / yesrefusedThis is a SURFnet nameserver - dns-beheer@surf.nl
ns2.surfnet.nl 192.87.36.2NOERROR, 13 ms, authoritativenoyes / yesrefusedThis is a SURFnet nameserver - dns-beheer@surfnet.nl
ns2.surfnet.nl 2001:610:3:200a:192:87:36:2NOERROR, 12 ms, authoritativenoyes / yesrefusedThis is a SURFnet nameserver - dns-beheer@surfnet.nl
ns3.surfnet.nl 195.169.124.71NOERROR, 10 ms, authoritativenoyes / yesrefusedThis is a SURFnet nameserver - dns-beheer@surfnet.nl
ns3.surfnet.nl 2001:610:0:800c:195:169:124:71NOERROR, 10 ms, authoritativenoyes / yesrefusedThis is a SURFnet nameserver - dns-beheer@surfnet.nl

Checks

  • ✓ All respond #14
    All 8 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"; ns1.zurich.surf.net: "This is a SURFnet nameserver - dns-beheer@surf.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.

SOA

pass

serial 2025153136 · primary ns1.surfnet.nl

Found

Primary (MNAME)
ns1.surfnet.nl
Contact (RNAME)
postmaster.duo.nl
Serial
2025153136
Refresh / retry
1200 s / 120 s
Expire
1209600 s
Negative TTL
86400 s

Serial per nameserver

NameserverSerial
ns1.surfnet.nl (192.87.106.101)2025153136
ns1.surfnet.nl (2001:610:1:800a:192:87:106:101)2025153136
ns1.zurich.surf.net (195.176.255.9)2025153136
ns1.zurich.surf.net (2001:620:0:9::1103)2025153136
ns2.surfnet.nl (192.87.36.2)2025153136
ns2.surfnet.nl (2001:610:3:200a:192:87:36:2)2025153136
ns3.surfnet.nl (195.169.124.71)2025153136
ns3.surfnet.nl (2001:610:0:800c:195:169:124:71)2025153136

Checks

  • ✓ Serial 2025153136 everywhere #22
    All nameservers serve the same version of the zone.
  • ✓ Timers within recommendations #23
    SOA refresh 20m, retry 2m, expire 14d, negative TTL 1d.
  • ✓ Primary is a public nameserver #24
    The primary nameserver ns1.surfnet.nl is one of the listed nameservers.
  • ✓ Contact postmaster@duo.nl #25
    The SOA RNAME postmaster.duo.nl means postmaster@duo.nl.
  • ✓ Timestamp serial #26
    The serial 2025153136 is a Unix timestamp (2034-03-05 06:32 UTC).

DNSSEC

warn

Signed, DS published at parent

Found

Validated by resolver
yes
Denial of existence
NSEC3
NSEC3
10 iterations, 7-byte salt
Signatures valid until
25 October 2026

DS at the parent

Key tagAlgorithmDigestMatches a key
30434RSASHA256 (8)SHA256 F4B1235C7A6C9E79…yes

DNSKEY in the zone

Key tagRoleAlgorithm
30434KSK (257)RSASHA256 (8)
20343ZSK (256)RSASHA256 (8)
14711KSK (257)RSASHA256 (8)

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 30434 (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 2026-10-21 16:21 UTC and expires at 2026-10-25 16:55 UTC.
  • !
    NSEC3 with extra iterations or salt
    NSEC3 uses 10 iterations and a 7-byte salt. RFC 9276 recommends 0 iterations and no salt: extra iterations cost resolvers CPU and add no real protection, and some validators treat high counts as insecure.
    #31

Records

pass

36 records at the apex

Found

Read from
192.87.106.101:53
TypeValueTTL
SOAns1.surfnet.nl. postmaster.duo.nl. 2025153136 1200 120 1209600 86400900
NSns3.surfnet.nl.900
NSns1.surfnet.nl.900
NSns2.surfnet.nl.900
NSns1.zurich.surf.net.900
A194.171.77.135900
AAAA2001:67c:262c:860::135900
MX10 grnms101.duo.nl.900
MX10 grnms102.duo.nl.900
TXT"google-site-verification=CUypQ0HV90dDVOrwS7D_vZ5NAk5lR02MgwbedEEYa1Y"900
TXT"apple-domain-verification=fFfN7j339skh0Mh1"900
TXT"v=spf1 mx a ip4:62.112.225.180 ip4:89.221.178.154 ip4:212.159.201.77 ip4:212.159.201.78 include:spf.protection.outlook.com ~all"900
TXT"e344b6293aaff980dacfdfca8d89a596c998a653ffc6da246984b5280553f353"900
TXT"cisco-ci-domain-verification=638367e007ac0876e9c860d9f73c3ed446324f61139de9b6cd0dc6c9900eea58"900
TXT"google-site-verification=qbvg5XNKlJSM6IZoZS_DoWYYvVN1177Tbwgn6PzPVFA"900
TXT"QuoVadis=25dc9442-0d2e-4179-afca-2f1a244a008c"900
TXT"MS=2A35729DF7B6879605A380199134229FA98192DC"900
TXT"d365mktkey=ZrTWozr5a3vpqbxt1Y3zYMwc3dTiPfefusQ5DUarTSUx"900
TXT"_jv1c8udejn31blgz6tm21crhud4cc4w"900
TXT"093013cdf61fd81ceca2a8b82df8d689d4a14ee58dd6ceb2c6ee38dde8e54e64"900
TXT"34795ab8189f9058900af51f79e50414a2d9a007be11677d35d79d4ed8b6cedf"900
TXT"google-site-verification=Jo-BbRZ-__HSKjce2cgIuEUi9tJDMMeuwuEVpl3Am9o"900
TXT"d365mktkey=V2SPaBFMsv3Px7EpOMn0EMJiGZjfArbfR9eOKlOWfLAx"900
TXT"kbE5rD5eSyaHC4KGPYtyK5pCrPFl3JLV1RvtjAkZolz8KyIMfpQEtYdL1kptnP0S"900
TXT"miro-verification=747ea291dc9933216b3ee89c85d886bb58e5ff2a"900
TXT"d365mktkey=Y2bbSTDjtCiPr1RmTDNbAt4t0K0xZ4voo8WTHuqtyhQx"900
TXT"cisco-ci-domain-verification=7720fd0785f14f8beee922a0084b84c2860b61ef66200ff3d739a4447472d9f4"900
TXT"_j006jnihj6zmhuldygm2l4yyqb3s5vm"900
TXT"8ZMdLGut+ODreQqgOL1z8ZPHCd32IZK5ee6DxdmpU/hZN9m7//YfHQhiDc9LcNQh1WZE9bbnbtsDyf2AGiFrQg=="900
CAA0 issue "quovadisglobal.com"900
CAA0 issue "kpn.com"900
CAA0 issuewild "digicert.com"900
CAA0 issue "www.pkioverheid.nl"900
CAA0 issue "www.digicert.com"900
CAA0 issue "certsign.ro"900
CAA0 issue "digicert.com"900

Checks

  • ✓ TTLs within range #32
    TTLs: A 15m, AAAA 15m, MX 15m, NS 15m. The NS TTL at the parent is 1h and in the zone 15m; 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.
  • ✓ CAA restricts issuance #35
    Certificates may be issued by: quovadisglobal.com, kpn.com, digicert.com, www.pkioverheid.nl, www.digicert.com, certsign.ro.