gfz-potsdam.de

Checked 21 October 2026, 22:40 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

ns.tu-berlin.de, zrt7b.gfz-potsdam.de

Found

Parent zone
de
Delegation from
a.nic.de (194.0.0.53)
NS at the parent
ns.tu-berlin.de, zrt7b.gfz-potsdam.de
NS in the zone
ns.tu-berlin.de, zrt7b.gfz-potsdam.de
NameserverAddressesNetwork (AS)Glue
ns.tu-berlin.de130.149.7.7 2001:638:809:7::7AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE130.149.7.7 2001:638:809:7::7
zrt7b.gfz-potsdam.de139.17.228.229AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE139.17.228.229

Checks

  • i
    2 nameservers
    Two nameservers meet the minimum; RFC 2182 recommends three or more for important zones: ns.tu-berlin.de, zrt7b.gfz-potsdam.de.
    #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: zrt7b.gfz-potsdam.de.
  • ✓ 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 2 IPv4 /24s and 1 IPv6 /48.
  • i
    All nameservers in one AS
    All nameserver addresses are announced by one network operator (AS680 (DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE): 3 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 .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: zrt7b.gfz-potsdam.de.
    #13

Nameservers

pass

3 of 3 addresses answer authoritatively

Found

NameserverAnswerRecursionTCP / EDNSAXFRVersion
ns.tu-berlin.de 130.149.7.7NOERROR, 13 ms, authoritativenoyes / yesrefused-
ns.tu-berlin.de 2001:638:809:7::7NOERROR, 14 ms, authoritativenoyes / yesrefused-
zrt7b.gfz-potsdam.de 139.17.228.229NOERROR, 13 ms, authoritativenoyes / yesrefused-

Checks

  • ✓ All respond #14
    All 3 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 2026101900 · primary zrt7b.gfz-potsdam.de

Found

Primary (MNAME)
zrt7b.gfz-potsdam.de
Contact (RNAME)
its-ddi.gfz.de
Serial
2026101900
Refresh / retry
14400 s / 3600 s
Expire
2592000 s
Negative TTL
3600 s

Serial per nameserver

NameserverSerial
ns.tu-berlin.de (130.149.7.7)2026101900
ns.tu-berlin.de (2001:638:809:7::7)2026101900
zrt7b.gfz-potsdam.de (139.17.228.229)2026101900

Checks

  • ✓ Serial 2026101900 everywhere #22
    All nameservers serve the same version of the zone.
  • ✓ Timers within recommendations #23
    SOA refresh 4h, retry 1h, expire 30d, negative TTL 1h.
  • ✓ Primary is a public nameserver #24
    The primary nameserver zrt7b.gfz-potsdam.de is one of the listed nameservers.
  • ✓ Contact its-ddi@gfz.de #25
    The SOA RNAME its-ddi.gfz.de means its-ddi@gfz.de.
  • ✓ Date-based serial #26
    The serial 2026101900 follows the YYYYMMDDnn convention (2026-10-19).

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

pass

21 records at the apex

Found

Read from
130.149.7.7:53
TypeValueTTL
SOAzrt7b.gfz-potsdam.de. its-ddi.gfz.de. 2026101900 14400 3600 2592000 360010800
NSns.tu-berlin.de.86400
NSzrt7b.gfz-potsdam.de.86400
A139.17.229.1510800
MX10 a1791.mx.srv.dfn.de.600
MX10 b1791.mx.srv.dfn.de.600
MX10 c1791.mx.srv.dfn.de.600
TXT"google-site-verification=gbS63fzs8bE6n0poYa1SDdFbwQm9V685MzGsLB54MX8"10800
TXT"v=spf1 a:mail.gfz-potsdam.de a:otc-de-spf.mms.t-systems-service.com a:gfz-potsdam.managed-otrs.com ~all"10800
TXT"HARICA-C4fL6G16WlrZVVnHzkk"10800
TXT"anthropic-domain-verification-j04wav=E6JALDWjIimAzEVFNCDjotjoW"10800
TXT"HARICA-V6Apl9oRFGtG4wdhwPJ"10800
TXT"HARICA-kCGm3uNXt57A201dL8P"10800
TXT"ZOOM_verify_CrllNFoaSz-ueCpdG5kw5Q"10800
TXT"apple-domain-verification=ccIO5azzaBaa6TcV"10800
TXT"MS=05F96486DA61AEC028E58EB3C15EDE435221E370"10800
TXT"brevo-code:6fad695b8997745705f7bded854ca36f"10800
TXT"google-site-verification=RvjA1HesvuxNyikUZSDgH5E0TPFVW7CSxArTjUrBLV8"10800
CAA0 issue "harica.gr"10800
CAA0 issue "pki.dfn.de"10800
CAA0 issue "sectigo.com"10800

Checks

  • ✓ TTLs within range #32
    TTLs: A 3h, MX 10m, NS 1d.
  • ✓ 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: harica.gr, pki.dfn.de, sectigo.com.