uni-potsdam.de

Checked 22 October 2026, 00:50 UTC · via 8.8.8.8
✗Problems found
21 passed 1 warning 1 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, dns-3.dfn.de, ns1.uni-potsdam.de, ns2.uni-potsdam.de

Found

Parent zone
de
Delegation from
a.nic.de (194.0.0.53)
NS at the parent
deneb.dfn.de, dns-3.dfn.de, ns1.uni-potsdam.de, ns2.uni-potsdam.de
NS in the zone
deneb.dfn.de, dns-3.dfn.de, ns1.uni-potsdam.de, ns2.uni-potsdam.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-
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-
ns1.uni-potsdam.de141.89.64.1 2001:638:807:40::2AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE141.89.64.1 2001:638:807:40::2
ns2.uni-potsdam.de141.89.65.1 2001:638:807:41::2AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE141.89.65.1 2001:638:807:41::2

Checks

  • ✓ 4 nameservers #6
    Delegated to deneb.dfn.de, dns-3.dfn.de, ns1.uni-potsdam.de, ns2.uni-potsdam.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.uni-potsdam.de, ns2.uni-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 4 IPv4 /24s and 3 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): 8 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
  • ✓ All reachable over IPv6 #13
    Every nameserver has an IPv6 address.

Nameservers

fail

7 of 8 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
dns-3.dfn.de 193.174.75.58NOERROR, 10 ms, authoritativenoyes / yesrefused0
dns-3.dfn.de 2001:638:d:b103::1NOERROR, 8 ms, authoritativenoyes / yesrefused0
ns1.uni-potsdam.de 141.89.64.1NOERROR, 13 ms, authoritativenoyes / yesrefused-
ns1.uni-potsdam.de 2001:638:807:40::2no responsenono / no--
ns2.uni-potsdam.de 141.89.65.1NOERROR, 14 ms, authoritativenoyes / yesrefused-
ns2.uni-potsdam.de 2001:638:807:41::2NOERROR, 13 ms, authoritativenoyes / yesrefused-

Checks

  • ✗
    Nameservers not responding
    These addresses did not answer, so resolvers waste time on timeouts: ns1.uni-potsdam.de (2001:638:807:40::2): read udp [2a01:4f8:1c1c:eebf::1]:59482->[2001:638:807:40::2]:53: i/o timeout.
    #14
  • ✓ 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: deneb.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

pass

serial 2024121293 · primary ns1.uni-potsdam.de

Found

Primary (MNAME)
ns1.uni-potsdam.de
Contact (RNAME)
root.rz.uni-potsdam.de
Serial
2024121293
Refresh / retry
10800 s / 3600 s
Expire
2419200 s
Negative TTL
900 s

Serial per nameserver

NameserverSerial
deneb.dfn.de (192.76.176.9)2024121293
deneb.dfn.de (2001:638:800:1::9)2024121293
dns-3.dfn.de (193.174.75.58)2024121293
dns-3.dfn.de (2001:638:d:b103::1)2024121293
ns1.uni-potsdam.de (141.89.64.1)2024121293
ns2.uni-potsdam.de (141.89.65.1)2024121293
ns2.uni-potsdam.de (2001:638:807:41::2)2024121293

Checks

  • ✓ Serial 2024121293 everywhere #22
    All nameservers serve the same version of the zone.
  • ✓ Timers within recommendations #23
    SOA refresh 3h, retry 1h, expire 28d, negative TTL 15m.
  • ✓ Primary is a public nameserver #24
    The primary nameserver ns1.uni-potsdam.de is one of the listed nameservers.
  • ✓ Contact root@rz.uni-potsdam.de #25
    The SOA RNAME root.rz.uni-potsdam.de means root@rz.uni-potsdam.de.
  • ✓ Date-based serial #26
    The serial 2024121293 follows the YYYYMMDDnn convention (2024-12-12).

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

19 records at the apex

Found

Read from
192.76.176.9:53
TypeValueTTL
SOAns1.uni-potsdam.de. root.rz.uni-potsdam.de. 2024121293 10800 3600 2419200 90028800
NSdns-3.dfn.de.28800
NSns1.uni-potsdam.de.28800
NSns2.uni-potsdam.de.28800
NSdeneb.dfn.de.28800
A141.89.239.528800
MX10 smtpin.uni-potsdam.de.28800
MX50 mx2.uni-potsdam.de.28800
MX40 mx1.uni-potsdam.de.28800
MX20 smtpin2.uni-potsdam.de.28800
TXT"_telesec-domain-validation=349631_2025-11-17_HNwcLkh03Ddy1qHs7A6aygcEJNVEHPiUW7N7R7Bnw0DvKHUiLu"28800
TXT"v=spf1 ip4:141.89.0.0/16 -all"28800
TXT"MS=45E3C90905CC87EE8DF150679F8ADA75DAEBF47B"28800
TXT"academiccloud-site-verification=fX4fFGC4txexdRZX4YDeJJDsq"28800
TXT"google-site-verification=ZPdU16_maEnCAzHFl-8Bvx9SKmjCDC4CnJ80hVWQBRU"28800
TXT"apple-domain-verification=Gh1qmp8sA17o8ZvN"28800
TXT"HARICA-ZbuCl6xDcK1Wli4u6eD"28800
TXT"google-site-verification=bvFklgX2769oDkgPohNT--p0EbinjjxjiPBYhYIeyB8"28800
TXT"ab4be8ed12551736a76278b3402d8559"28800

Checks

  • ✓ TTLs within range #32
    TTLs: A 8h, MX 8h, NS 8h. The NS TTL at the parent is 1d and in the zone 8h; 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