difu.de

Checked 21 October 2026, 22:14 UTC · via 8.8.8.8
!Passed with warnings
19 passed 4 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

deneb.dfn.de, ns.difu.de, ns.tu-berlin.de

Found

Parent zone
de
Delegation from
a.nic.de (194.0.0.53)
NS at the parent
deneb.dfn.de, ns.difu.de, ns.tu-berlin.de
NS in the zone
deneb.dfn.de, ns.difu.de, ns.tu-berlin.de
NameserverAddressesNetwork (AS)Glue
deneb.dfn.de192.76.176.9 2001:638:800:1::9AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE-
ns.difu.de194.95.152.98AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE194.95.152.98
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

Checks

  • ✓ 3 nameservers #6
    Delegated to deneb.dfn.de, ns.difu.de, ns.tu-berlin.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: ns.difu.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 3 IPv4 /24s and 2 IPv6 /48s.
  • 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): 5 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: ns.difu.de.
    #13

Nameservers

warn

5 of 5 addresses answer authoritatively

Found

NameserverAnswerRecursionTCP / EDNSAXFRVersion
deneb.dfn.de 192.76.176.9NOERROR, 14 ms, authoritativenoyes / yesrefused0
deneb.dfn.de 2001:638:800:1::9NOERROR, 14 ms, authoritativenoyes / yesrefused0
ns.difu.de 194.95.152.98NOERROR, 13 ms, authoritativenoyes / yesrefused9.20.29-1~deb13u1-Debian
ns.tu-berlin.de 130.149.7.7NOERROR, 13 ms, authoritativenoyes / yesrefused-
ns.tu-berlin.de 2001:638:809:7::7NOERROR, 13 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.
  • !
    Software version disclosed
    These nameservers report their software version via version.bind/version.server, which helps attackers find known vulnerabilities: ns.difu.de: "9.20.29-1~deb13u1-Debian". Hide or replace the version string.
    #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

warn

serial 2026081101 · primary ns.difu.de

Found

Primary (MNAME)
ns.difu.de
Contact (RNAME)
hostmaster.difu.de
Serial
2026081101
Refresh / retry
10800 s / 14400 s
Expire
2419200 s
Negative TTL
600 s

Serial per nameserver

NameserverSerial
deneb.dfn.de (192.76.176.9)2026081101
deneb.dfn.de (2001:638:800:1::9)2026081101
ns.difu.de (194.95.152.98)2026081101
ns.tu-berlin.de (130.149.7.7)2026081101
ns.tu-berlin.de (2001:638:809:7::7)2026081101

Checks

  • ✓ Serial 2026081101 everywhere #22
    All nameservers serve the same version of the zone.
  • !
    Unusual SOA timers
    retry 4h should be shorter than refresh 3h. Current values: refresh 3h, retry 4h, expire 28d, negative TTL 10m.
    #23
  • ✓ Primary is a public nameserver #24
    The primary nameserver ns.difu.de is one of the listed nameservers.
  • ✓ Contact hostmaster@difu.de #25
    The SOA RNAME hostmaster.difu.de means hostmaster@difu.de.
  • ✓ Date-based serial #26
    The serial 2026081101 follows the YYYYMMDDnn convention (2026-08-11).

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

13 records at the apex

Found

Read from
192.76.176.9:53
TypeValueTTL
SOAns.difu.de. hostmaster.difu.de. 2026081101 10800 14400 2419200 6003600
NSns.tu-berlin.de.86400
NSdeneb.dfn.de.86400
NSns.difu.de.86400
A194.95.152.7560
MX10 b1221.mx.srv.dfn.de.3600
MX10 a1221.mx.srv.dfn.de.3600
MX10 c1221.mx.srv.dfn.de.3600
TXT"adobe-idp-site-verification=d190c0caf4d540c8655ebce062f5df1e0c02a9b09ae2293142e2b5f6968ad3e2"3600
TXT"google-site-verification=LzxgXRXu_JxT2MZF15yF0qS7pAKj1lL_GqRnQb1DUfY"3600
TXT"v=spf1 ip4:194.95.152.96 include:_spf.o122.mx.srv.dfn.de include:spfhard.crsend.com -all"3600
TXT"MS=6615E3D3795CBB4C44239F754E9F7113859DC0E1"3600
TXT"linkedin-site-verification=43ccc6a8-c836-4f57-b81d-2bce5d3be7c8"3600

Checks

  • !
    Very low TTLs
    These records have a TTL below 5m, causing extra queries and slower lookups: A (1m). Low TTLs are useful just before a planned change.
    #32
  • ✓ 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