fh-potsdam.de

Checked 21 October 2026, 22:20 UTC · via 8.8.8.8
!Passed with warnings
21 passed 4 warnings 0 failed 4 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

dns-1.dfn.de, dns-2.dfn.de, dns-3.dfn.de, ns.fh-potsdam.de

Found

Parent zone
de
Delegation from
a.nic.de (194.0.0.53)
NS at the parent
dns-1.dfn.de, dns-2.dfn.de, dns-3.dfn.de, ns.fh-potsdam.de
NS in the zone
dns-1.dfn.de, dns-2.dfn.de, dns-3.dfn.de, ns.fh-potsdam.de
NameserverAddressesNetwork (AS)Glue
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-2.dfn.de193.174.75.54 2001:638:d:b102::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-
ns.fh-potsdam.de193.175.28.2 2001:638:81c::53AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE193.175.28.2 2001:638:81c::53

Checks

  • ✓ 4 nameservers #6
    Delegated to dns-1.dfn.de, dns-2.dfn.de, dns-3.dfn.de, ns.fh-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: ns.fh-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 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): 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

warn

8 of 8 addresses answer authoritatively

Found

NameserverAnswerRecursionTCP / EDNSAXFRVersion
dns-1.dfn.de 193.174.75.50NOERROR, 12 ms, authoritativenoyes / yesrefused0
dns-1.dfn.de 2001:638:d:b101::1NOERROR, 12 ms, authoritativenoyes / yesrefused0
dns-2.dfn.de 193.174.75.54NOERROR, 7 ms, authoritativenoyes / yesrefused0
dns-2.dfn.de 2001:638:d:b102::1NOERROR, 7 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
ns.fh-potsdam.de 193.175.28.2NOERROR, 17 ms, authoritativenoyes / yesrefusedPowerDNS Authoritative Server 5.1.5 (built Oct 7 2026 06:12:54 by root@localhost)
ns.fh-potsdam.de 2001:638:81c::53NOERROR, 13 ms, authoritativenoyes / yesrefusedPowerDNS Authoritative Server 5.1.5 (built Oct 7 2026 06:12:54 by root@localhost)

Checks

  • ✓ All respond #14
    All 8 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.fh-potsdam.de: "PowerDNS Authoritative Server 5.1.5 (built Oct 7 2026 06:12:54 by root@localhost)". 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 2026105064 · primary ns.fh-potsdam.de

Found

Primary (MNAME)
ns.fh-potsdam.de
Contact (RNAME)
it-service.fh-potsdam.de
Serial
2026105064
Refresh / retry
28800 s / 7200 s
Expire
604800 s
Negative TTL
172800 s

Serial per nameserver

NameserverSerial
dns-1.dfn.de (193.174.75.50)2026105064
dns-1.dfn.de (2001:638:d:b101::1)2026105064
dns-2.dfn.de (193.174.75.54)2026105064
dns-2.dfn.de (2001:638:d:b102::1)2026105064
dns-3.dfn.de (193.174.75.58)2026105064
dns-3.dfn.de (2001:638:d:b103::1)2026105064
ns.fh-potsdam.de (193.175.28.2)2026105064
ns.fh-potsdam.de (2001:638:81c::53)2026105064

Checks

  • ✓ Serial 2026105064 everywhere #22
    All nameservers serve the same version of the zone.
  • !
    Unusual SOA timers
    negative caching TTL (minimum) 2d is outside 5m–1d (RFC 2308 recommends 1–3 hours). Current values: refresh 8h, retry 2h, expire 7d, negative TTL 2d.
    #23
  • ✓ Primary is a public nameserver #24
    The primary nameserver ns.fh-potsdam.de is one of the listed nameservers.
  • ✓ Contact it-service@fh-potsdam.de #25
    The SOA RNAME it-service.fh-potsdam.de means it-service@fh-potsdam.de.
  • ✓ Timestamp serial #26
    The serial 2026105064 is a Unix timestamp (2034-03-16 06:57 UTC).

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

22 records at the apex

Found

Read from
193.174.75.50:53
TypeValueTTL
SOAns.fh-potsdam.de. it-service.fh-potsdam.de. 2026105064 28800 7200 604800 1728003600
NSns.fh-potsdam.de.3600
NSdns-3.dfn.de.3600
NSdns-2.dfn.de.3600
NSdns-1.dfn.de.3600
A193.175.28.523600
AAAA2001:638:81c::28:523600
MX0 fhpotsdam-de0e.mail.protection.outlook.com.60
TXT"6d67014b72cd13f06a4da619a4273da6"60
TXT"ZOOM_verify_yzsF0aDkSu6vRfQCL11jIw"60
TXT"v=spf1 mx mx:s1902.mx.srv.dfn.de ip4:193.175.28.0/24 ip6:2001:638:81c:0::/64 include:spf.protection.outlook.com -all"60
TXT"google-site-verification=sUch_8bCuxiCYMShprw7CG1cRLJCq40Ltux0xKBQ-6k"60
TXT"adobe-idp-site-verification=b1ac341cfa94919b02f11cf660fdde2ad5744ec0f3b38d1f1b58584124c04dc6"60
TXT"2af13c595471c4ade259985bd989977c"60
TXT"MS=ms35429193"60
TXT"apple-domain-verification=QxM64y4E3pcpNaHW"60
TXT"HARICA-qjUcFhZMrgfiz4pYRZ0"60
CAA0 issue "harica.gr"60
CAA0 issuemail "harica.gr"60
CAA0 iodef "mailto:ca@fh-potsdam.de"60
CAA0 issue "letsencrypt.org"60
CAA0 issuewild "harica.gr"60

Checks

  • !
    Very low TTLs
    These records have a TTL below 5m, causing extra queries and slower lookups: MX (1m). Low TTLs are useful just before a planned change. The NS TTL at the parent is 1d and in the zone 1h; resolvers may use either.
    #32
  • ✓ 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, letsencrypt.org.