ioer.de

Checked 21 October 2026, 23:00 UTC · via 8.8.8.8
!Passed with warnings
18 passed 2 warnings 0 failed 9 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

adns1.zih.tu-dresden.de, adns2.zih.tu-dresden.de, dns-1.dfn.de, dns-3.dfn.de

Found

Parent zone
de
Delegation from
a.nic.de (194.0.0.53)
NS at the parent
adns1.zih.tu-dresden.de, adns2.zih.tu-dresden.de, dns-1.dfn.de, dns-3.dfn.de
NS in the zone
adns1.zih.tu-dresden.de, adns2.zih.tu-dresden.de, dns-1.dfn.de, dns-3.dfn.de
NameserverAddressesNetwork (AS)Glue
adns1.zih.tu-dresden.de141.30.67.53AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE141.30.67.53
adns2.zih.tu-dresden.de141.76.32.53AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE141.76.32.53
dns-1.dfn.de193.174.75.50 2001:638:d:b101::1AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE-
dns-3.dfn.de193.174.75.58 2001:638:d:b103::1AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE-

Checks

  • ✓ 4 nameservers #6
    Delegated to adns1.zih.tu-dresden.de, adns2.zih.tu-dresden.de, dns-1.dfn.de, dns-3.dfn.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 2001:638:d::/48, while the other address family is spread over several networks.
    #10
  • 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): 6 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: adns1.zih.tu-dresden.de, adns2.zih.tu-dresden.de.
    #13

Nameservers

info

6 of 6 addresses answer authoritatively

Found

NameserverAnswerRecursionTCP / EDNSAXFRVersion
adns1.zih.tu-dresden.de 141.30.67.53NOERROR, 14 ms, authoritativenoyes / yesrefused0
adns2.zih.tu-dresden.de 141.76.32.53NOERROR, 14 ms, authoritativenoyes / yesrefused0
dns-1.dfn.de 193.174.75.50NOERROR, 14 ms, authoritativenoyes / yesrefused0
dns-1.dfn.de 2001:638:d:b101::1NOERROR, 13 ms, authoritativenoyes / yesrefused0
dns-3.dfn.de 193.174.75.58NOERROR, 8 ms, authoritativenoyes / yesrefused0
dns-3.dfn.de 2001:638:d:b103::1NOERROR, 8 ms, authoritativenoyes / yesrefused0

Checks

  • ✓ All respond #14
    All 6 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.
  • i
    Identifying string disclosed
    These nameservers answer version queries with a string that is not a version number: adns1.zih.tu-dresden.de: "0"; adns2.zih.tu-dresden.de: "0"; dns-1.dfn.de: "0"; dns-3.dfn.de: "0".
    #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 2036102100 · primary pdns1.zih.tu-dresden.de

Found

Primary (MNAME)
pdns1.zih.tu-dresden.de
Contact (RNAME)
hostmaster.tu-dresden.de
Serial
2036102100
Refresh / retry
21600 s / 3600 s
Expire
2419200 s
Negative TTL
3600 s

Serial per nameserver

NameserverSerial
adns1.zih.tu-dresden.de (141.30.67.53)2036102100
adns2.zih.tu-dresden.de (141.76.32.53)2036102100
dns-1.dfn.de (193.174.75.50)2036102100
dns-1.dfn.de (2001:638:d:b101::1)2036102100
dns-3.dfn.de (193.174.75.58)2036102100
dns-3.dfn.de (2001:638:d:b103::1)2036102100

Checks

  • ✓ Serial 2036102100 everywhere #22
    All nameservers serve the same version of the zone.
  • ✓ Timers within recommendations #23
    SOA refresh 6h, retry 1h, expire 28d, negative TTL 1h.
  • i
    Hidden master
    The primary nameserver pdns1.zih.tu-dresden.de is not listed as a nameserver: a hidden master that only feeds the public secondaries. That is a common setup; make sure it is not reachable for zone transfers from outside.
    #24
  • ✓ Contact hostmaster@tu-dresden.de #25
    The SOA RNAME hostmaster.tu-dresden.de means hostmaster@tu-dresden.de.
  • !
    Serial date in the future
    The serial 2036102100 looks like a date (YYYYMMDDnn) in the future (2036-10-21). It can only grow, so a wrong date can't be undone without a serial wrap-around.
    #26

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

14 records at the apex

Found

Read from
141.30.67.53:53
TypeValueTTL
SOApdns1.zih.tu-dresden.de. hostmaster.tu-dresden.de. 2036102100 21600 3600 2419200 360086400
NSdns-3.dfn.de.86400
NSadns1.zih.tu-dresden.de.86400
NSadns2.zih.tu-dresden.de.86400
NSdns-1.dfn.de.86400
A134.119.225.17786400
AAAA2a00:116a:10f:7b70::86400
MX20 mailin-sek1.zih.tu-dresden.de.3600
MX20 mailin-prim2.zih.tu-dresden.de.3600
MX20 mailin-prim1.zih.tu-dresden.de.3600
TXT"canva-site-verification=cXUmBZoCy-ngyFlH1Qo5jQ"86400
TXT"ZOOM_verify_jbu2t1cBFZqNtqT50esObp"86400
TXT"adobe-idp-site-verification=a8f160a7ecb76bef98d684d520b973b0d8b810bf1f1d57908e1cb2686991d623"86400
TXT"v=spf1 include:mail.ioer.de include:spf.crsend.com ip4:193.174.15.10 ~all"86400

Checks

  • ✓ TTLs within range #32
    TTLs: A 1d, AAAA 1d, MX 1h, 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.
  • 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