koeln-bonn-airport.de

Checked 21 October 2026, 23:10 UTC · via 8.8.8.8
!Passed with warnings
21 passed 2 warnings 0 failed 6 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

info

dns3.netcologne.de, dns4.netcologne.de, dns5.netcologne.de

Found

Parent zone
de
Delegation from
a.nic.de (194.0.0.53)
NS at the parent
dns3.netcologne.de, dns4.netcologne.de, dns5.netcologne.de
NS in the zone
dns3.netcologne.de, dns4.netcologne.de, dns5.netcologne.de
NameserverAddressesNetwork (AS)Glue
dns3.netcologne.de213.196.239.187 2001:4dd0:100:1029:53:3:0:3AS8422 NETCOLOGNE - NetCologne Gesellschaft fur Telekommunikation mbH, DE AS8422 NETCOLOGNE - NetCologne Gesellschaft fur Telekommunikation mbH, DE-
dns4.netcologne.de195.14.247.116 2001:4dd0:100:4220:53:4:0:4AS8422 NETCOLOGNE - NetCologne Gesellschaft fur Telekommunikation mbH, DE AS8422 NETCOLOGNE - NetCologne Gesellschaft fur Telekommunikation mbH, DE-
dns5.netcologne.de134.95.100.211AS5520 UNI-KOELN - Universitaet zu Koeln, DE-

Checks

  • ✓ 3 nameservers #6
    Delegated to dns3.netcologne.de, dns4.netcologne.de, dns5.netcologne.de.
  • ✓ 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.
  • i
    One address family in one network
    all IPv6 addresses are in 2001:4dd0:100::/48, while the other address family is spread over several networks.
    #10
  • ✓ 2 autonomous systems #11
    The nameservers are spread over: AS5520 (UNI-KOELN - Universitaet zu Koeln, DE): 1 address; AS8422 (NETCOLOGNE - NetCologne Gesellschaft fur Telekommunikation mbH, DE): 4 addresses.
  • i
    All nameserver names under .de
    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
  • i
    Partly IPv6
    These nameservers have no IPv6 address: dns5.netcologne.de.
    #13

Nameservers

pass

5 of 5 addresses answer authoritatively

Found

NameserverAnswerRecursionTCP / EDNSAXFRVersion
dns3.netcologne.de 213.196.239.187NOERROR, 7 ms, authoritativenoyes / yesrefused-
dns3.netcologne.de 2001:4dd0:100:1029:53:3:0:3NOERROR, 7 ms, authoritativenoyes / yesrefused-
dns4.netcologne.de 195.14.247.116NOERROR, 7 ms, authoritativenoyes / yesrefused-
dns4.netcologne.de 2001:4dd0:100:4220:53:4:0:4NOERROR, 7 ms, authoritativenoyes / yesrefused-
dns5.netcologne.de 134.95.100.211NOERROR, 11 ms, authoritativenoyes / yesrefused-

Checks

  • ✓ All respond #14
    All 5 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.
  • ✓ 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 2024062071 · primary dns3.netcologne.de

Found

Primary (MNAME)
dns3.netcologne.de
Contact (RNAME)
hostmaster.netcologne.de
Serial
2024062071
Refresh / retry
300 s / 3600 s
Expire
2419200 s
Negative TTL
900 s

Serial per nameserver

NameserverSerial
dns3.netcologne.de (213.196.239.187)2024062071
dns3.netcologne.de (2001:4dd0:100:1029:53:3:0:3)2024062071
dns4.netcologne.de (195.14.247.116)2024062071
dns4.netcologne.de (2001:4dd0:100:4220:53:4:0:4)2024062071
dns5.netcologne.de (134.95.100.211)2024062071

Checks

  • ✓ Serial 2024062071 everywhere #22
    All nameservers serve the same version of the zone.
  • !
    Unusual SOA timers
    refresh 5m is outside 20m–1d; retry 1h should be shorter than refresh 5m. Current values: refresh 5m, retry 1h, expire 28d, negative TTL 15m.
    #23
  • ✓ Primary is a public nameserver #24
    The primary nameserver dns3.netcologne.de is one of the listed nameservers.
  • ✓ Contact hostmaster@netcologne.de #25
    The SOA RNAME hostmaster.netcologne.de means hostmaster@netcologne.de.
  • ✓ Date-based serial #26
    The serial 2024062071 follows the YYYYMMDDnn convention (2024-06-20).

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

info

16 records at the apex

Found

Read from
213.196.239.187:53
TypeValueTTL
SOAdns3.netcologne.de. hostmaster.netcologne.de. 2024062071 300 3600 2419200 900600
NSdns3.netcologne.de.600
NSdns5.netcologne.de.600
NSdns4.netcologne.de.600
MX20 mail1.koeln-bonn-airport.de.600
MX20 mail2.koeln-bonn-airport.de.600
TXT"knowbe4-site-verification=3350564f9e9ab3c06c90725ad760b6df"600
TXT"WEuZh8ta+QaGpm1GTrhbo2gcIZCRpGNJwr74vzHNYUNp2keL6m6tMeFmQSTCQB54GeHszTgZ+SAFxqObTNyu/g=="600
TXT"google-site-verification=ZqQ3DmdCL9bpiSgB4IlUh3iIpXTxEgHQ_ft7haZBVSU"600
TXT"successfactors-site-verification=YjMwMjllNTRiMzE5Yjc4NTdlZjAyYTRiYTMwYzAwYWY5ZjQ2MmRjYzAwMjQ1MDFmZTYyN2U2ODE3MTFlOWVkNQ=="600
TXT"v=spf1 a mx a:cgn-nebenan.de include:spf.protection.outlook.com include:_spf.cmail.ondemand.com ip4:194.110.25.161 ip4:194.110.25.162 ip4:194.110.25.163 ip4:52.157.149.216 ip4:35.242.247.107 ip4:34.107.8.58 ip4:34.107.88.2 ip4:35.246.224.53 -all"600
TXT"MS=ms76377809"600
TXT"swisssign-check=l3W2TTPTHc9xbq0qYDF60KrsJGd0kqZPzogUWsC6OA"600
TXT"apple-domain-verification=3akrvkeA6sWeVqFc"600
TXT"_telesec-domain-validation=350425_2025-07-21_YJErEHiGkI6pADt34x6k5tkY9av3OXY8Hu6QYvuDBUn0aEU73r"600
TXT"d365mktkey=xgZx29SfAheW2SDpBsqX8sk9VqTtQtrHhxfyNmu0QQwx"600

Checks

  • ✓ TTLs within range #32
    TTLs: MX 10m, NS 10m. The NS TTL at the parent is 1d and in the zone 10m; 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