cdu.de

Checked 21 October 2026, 22:06 UTC · via 8.8.8.8
!Passed with warnings
22 passed 1 warning 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

ns1.arcor-ip.de, ns1.cdu.de, ns2.arcor-ip.de, ns3.arcor-ip.de

Found

Parent zone
de
Delegation from
a.nic.de (194.0.0.53)
NS at the parent
ns1.arcor-ip.de, ns1.cdu.de, ns2.arcor-ip.de, ns3.arcor-ip.de
NS in the zone
ns1.arcor-ip.de, ns1.cdu.de, ns2.arcor-ip.de, ns3.arcor-ip.de
NameserverAddressesNetwork (AS)Glue
ns1.arcor-ip.de145.253.2.144 2a01:860:0:202::53AS3209 VODANET - Vodafone GmbH, DE AS3209 VODANET - Vodafone GmbH, DE145.253.2.144 2a01:860:0:202::53
ns1.cdu.de193.219.105.58AS3320 DTAG - Deutsche Telekom AG, DE193.219.105.58
ns2.arcor-ip.de145.253.3.16 2a01:860:0:203::53AS3209 VODANET - Vodafone GmbH, DE AS3209 VODANET - Vodafone GmbH, DE145.253.3.16 2a01:860:0:203::53
ns3.arcor-ip.de145.253.3.20 2a01:860:0:204::53AS3209 VODANET - Vodafone GmbH, DE AS3209 VODANET - Vodafone GmbH, DE145.253.3.20 2a01:860:0:204::53

Checks

  • ✓ 4 nameservers #6
    Delegated to ns1.arcor-ip.de, ns1.cdu.de, ns2.arcor-ip.de, ns3.arcor-ip.de.
  • ✓ 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.cdu.de.
  • ✓ 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 2a01:860::/48, while the other address family is spread over several networks.
    #10
  • ✓ 2 autonomous systems #11
    The nameservers are spread over: AS3209 (VODANET - Vodafone GmbH, DE): 6 addresses; AS3320 (DTAG - Deutsche Telekom AG, DE): 1 address.
  • 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: ns1.cdu.de.
    #13

Nameservers

pass

7 of 7 addresses answer authoritatively

Found

NameserverAnswerRecursionTCP / EDNSAXFRVersion
ns1.arcor-ip.de 145.253.2.144NOERROR, 4 ms, authoritativenoyes / yesrefused-
ns1.arcor-ip.de 2a01:860:0:202::53NOERROR, 4 ms, authoritativenoyes / yesrefused-
ns1.cdu.de 193.219.105.58NOERROR, 9 ms, authoritativenoyes / yesrefused-
ns2.arcor-ip.de 145.253.3.16NOERROR, 11 ms, authoritativenoyes / yesrefused-
ns2.arcor-ip.de 2a01:860:0:203::53NOERROR, 11 ms, authoritativenoyes / yesrefused-
ns3.arcor-ip.de 145.253.3.20NOERROR, 9 ms, authoritativenoyes / yesrefused-
ns3.arcor-ip.de 2a01:860:0:204::53NOERROR, 9 ms, authoritativenoyes / yesrefused-

Checks

  • ✓ All respond #14
    All 7 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

pass

serial 2026102101 · primary ns1.cdu.de

Found

Primary (MNAME)
ns1.cdu.de
Contact (RNAME)
root.ns1.cdu.de
Serial
2026102101
Refresh / retry
10000 s / 1800 s
Expire
604800 s
Negative TTL
600 s

Serial per nameserver

NameserverSerial
ns1.arcor-ip.de (145.253.2.144)2026102101
ns1.arcor-ip.de (2a01:860:0:202::53)2026102101
ns1.cdu.de (193.219.105.58)2026102101
ns2.arcor-ip.de (145.253.3.16)2026102101
ns2.arcor-ip.de (2a01:860:0:203::53)2026102101
ns3.arcor-ip.de (145.253.3.20)2026102101
ns3.arcor-ip.de (2a01:860:0:204::53)2026102101

Checks

  • ✓ Serial 2026102101 everywhere #22
    All nameservers serve the same version of the zone.
  • ✓ Timers within recommendations #23
    SOA refresh 2h46m40s, retry 30m, expire 7d, negative TTL 10m.
  • ✓ Primary is a public nameserver #24
    The primary nameserver ns1.cdu.de is one of the listed nameservers.
  • ✓ Contact root@ns1.cdu.de #25
    The SOA RNAME root.ns1.cdu.de means root@ns1.cdu.de.
  • ✓ Date-based serial #26
    The serial 2026102101 follows the YYYYMMDDnn convention (2026-10-21).

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

18 records at the apex

Found

Read from
145.253.2.144:53
TypeValueTTL
SOAns1.cdu.de. root.ns1.cdu.de. 2026102101 10000 1800 604800 600600
NSns1.arcor-ip.de.600
NSns1.cdu.de.600
NSns3.arcor-ip.de.600
NSns2.arcor-ip.de.600
A193.219.105.10600
MX5 mail48.cdu.de.600
TXT"google-site-verification=uPtRpymmuYjbZQ1Lmr2a1gAdJuAGrEHOKCgG22YJNYA"600
TXT"apple-domain-verification=3SPyxSh5Gir4W3lC"600
TXT"google-site-verification=5VKRrUmBgFVF-szaRCFv4S0c4pajeEcqTBqvVSkNjlk"600
TXT"MS=ms80140043"600
TXT"MS=ms73549048"600
TXT"v=spf1 ip4:193.219.105.0/24 ip4:87.129.40.18 ip4:87.129.40.20 ip4:87.129.40.21 ip4:87.129.40.22 include:spf.protection.outlook.com include:inxserver.com include:spf.mailjet.com include:spf.sendinblue.com mx -all"600
TXT"Sendinblue-code:aa2789879467a12bc6861a37ecf4889f"600
TXT"NEcqxLZkjZv1JyFpDjTNF/wvWupIQoimBc6Gc+5SbtwxiXS/DOATFriP+92cb9SB4t9ZwSRS7aaXbPLqZzFnlg=="600
TXT"google-site-verification=GyUpyOQVmh5n3HahHS97DHNVkwwfaagmy9WKenpTEg8"600
TXT"google-site-verification=HxwmL2DD8zzNOeUQ4xOvXuYGwDJ6xM0Ws9eckrztXVw"600
TXT"cisco-ci-domain-verification=10a6638c06922ff7bf5c73c9899e3e6517bce78ae01ebb8f7892f319ab8c07d6"600

Checks

  • ✓ TTLs within range #32
    TTLs: A 10m, 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