lehrer-online.de

Checked 21 October 2026, 23:11 UTC · via 8.8.8.8
✗Problems found
19 passed 4 warnings 1 failed 5 info

Registration

info

.de country-code

Found

TLD
.de (country-code)
ICANN policies apply
no

Checks

  • i
    .de 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
    .de is delegated in the root zone and DNSSEC-signed.
  • i
    Registration data not available
    No registration data via RDAP: the registry of .de offers no RDAP service. Many ccTLD registries don't offer RDAP; check the registry's WHOIS instead.
    #3

Delegation

warn

ns1.oberdieck.com, ns2.oberdieck.com, ns3.oberdieck.com, ns4.oberdieck.com

Found

Parent zone
de
Delegation from
a.nic.de (194.0.0.53)
NS at the parent
ns1.oberdieck.com, ns2.oberdieck.com, ns3.oberdieck.com, ns4.oberdieck.com
NS in the zone
ns1.oberdieck.com, ns2.oberdieck.com, ns3.oberdieck.com, ns4.oberdieck.com
NameserverAddressesNetwork (AS)Glue
ns1.oberdieck.com95.130.16.246AS13246 INETWIRE-AS - Key-Systems GmbH, DE-
ns2.oberdieck.com95.130.17.218AS13246 INETWIRE-AS - Key-Systems GmbH, DE-
ns3.oberdieck.com217.146.22.194AS42473 AS-ANEXIA - Anexia Cloud Solutions GmbH, AT-
ns4.oberdieck.com144.76.91.137AS24940 HETZNER-AS - Hetzner Online GmbH, DE-

Checks

  • ✓ 4 nameservers #6
    Delegated to ns1.oberdieck.com, ns2.oberdieck.com, ns3.oberdieck.com, ns4.oberdieck.com.
  • ✓ 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 0 IPv6 /48s.
  • ✓ 3 autonomous systems #11
    The nameservers are spread over: AS13246 (INETWIRE-AS - Key-Systems GmbH, DE): 2 addresses; AS24940 (HETZNER-AS - Hetzner Online GmbH, DE): 1 address; AS42473 (AS-ANEXIA - Anexia Cloud Solutions GmbH, AT): 1 address.
  • i
    All nameserver names under .com
    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

Nameservers

fail

3 of 4 addresses answer authoritatively

Found

NameserverAnswerRecursionTCP / EDNSAXFRVersion
ns1.oberdieck.com 95.130.16.246no responsenono / no--
ns2.oberdieck.com 95.130.17.218NOERROR, 18 ms, authoritativenoyes / yesrefused-
ns3.oberdieck.com 217.146.22.194NOERROR, 4 ms, authoritativenoyes / yesrefused-
ns4.oberdieck.com 144.76.91.137NOERROR, 2 ms, authoritativenoyes / yesrefused-

Checks

  • ✗
    Nameservers not responding
    These addresses did not answer, so resolvers waste time on timeouts: ns1.oberdieck.com (95.130.16.246): read udp 46.225.38.91:38784->95.130.16.246:53: i/o timeout.
    #14
  • ✓ All authoritative #15
    Every responding nameserver answers authoritatively for the zone.
  • ✓ No recursion #16
    The nameservers do not answer recursive queries for other domains.
  • ✓ No version disclosed #17
    The nameservers don't reveal their software version.
  • ✓ 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

warn

serial 2026051901 · primary ns1.oberdieck.com

Found

Primary (MNAME)
ns1.oberdieck.com
Contact (RNAME)
hostmaster.internetwire.de
Serial
2026051901
Refresh / retry
28800 s / 7200 s
Expire
604800 s
Negative TTL
240 s

Serial per nameserver

NameserverSerial
ns2.oberdieck.com (95.130.17.218)2026051901
ns3.oberdieck.com (217.146.22.194)2026051901
ns4.oberdieck.com (144.76.91.137)2026051901

Checks

  • ✓ Serial 2026051901 everywhere #22
    All nameservers serve the same version of the zone.
  • !
    Unusual SOA timers
    negative caching TTL (minimum) 4m is outside 5m–1d (RFC 2308 recommends 1–3 hours). Current values: refresh 8h, retry 2h, expire 7d, negative TTL 4m.
    #23
  • ✓ Primary is a public nameserver #24
    The primary nameserver ns1.oberdieck.com is one of the listed nameservers.
  • ✓ Contact hostmaster@internetwire.de #25
    The SOA RNAME hostmaster.internetwire.de means hostmaster@internetwire.de.
  • ✓ Date-based serial #26
    The serial 2026051901 follows the YYYYMMDDnn convention (2026-05-19).

DNSSEC

warn

Not signed

Found

Validated by resolver
no

Checks

  • !
    Not signed
    The zone is not signed with DNSSEC, so answers can be spoofed. Enable DNSSEC at your DNS provider and publish the DS record at your registrar.
    #27

Records

warn

11 records at the apex

Found

Read from
95.130.17.218:53
TypeValueTTL
SOAns1.oberdieck.com. hostmaster.internetwire.de. 2026051901 28800 7200 604800 2403600
NSns1.oberdieck.com.3597
NSns2.oberdieck.com.3597
NSns3.oberdieck.com.3597
NSns4.oberdieck.com.3597
A138.201.50.2183600
AAAA2a01:4f8:172:be7::23600
MX10 lehreronline-de01e.mail.protection.outlook.com.240
TXT"MS=ms60762245"86400
TXT"v=spf1 a mx ptr ip4:89.191.78.0/24 ip4:82.165.112.33 include:spf.protection.outlook.com include:spf.crsend.com ip4:185.98.184.0/24 ip4:80.82.206.0/26 ip4:188.40.30.118 include:emsd1.com include:_spf.sendnode.com ~all"3600
TXT"stripe-verification=76dc71ac95a85885c3be9b47eb36163ef4d194f714b66f08658cbf9b74a15296"3600

Checks

  • !
    Very low TTLs
    These records have a TTL below 5m, causing extra queries and slower lookups: MX (4m). Low TTLs are useful just before a planned change. The NS TTL at the parent is 1d and in the zone 59m57s; resolvers may use either.
    #32
  • ✓ No CNAME at the apex #33
    The zone apex has no CNAME record.
  • i
    Wildcard record
    A random name under the zone resolves, so there is a wildcard (*) record. Typos and non-existent hosts resolve too, which can confuse mail and certificate checks.
    #34
  • 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