tu-cottbus.de

Checked 22 October 2026, 00:41 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.rz.tu-cottbus.de, dns2.sbone.tu-cottbus.de, math-s.math.tu-cottbus.de

Found

Parent zone
de
Delegation from
a.nic.de (194.0.0.53)
NS at the parent
deneb.dfn.de, dns.rz.tu-cottbus.de, dns2.sbone.tu-cottbus.de, math-s.math.tu-cottbus.de
NS in the zone
deneb.dfn.de, dns.rz.tu-cottbus.de, dns2.sbone.tu-cottbus.de, math-s.math.tu-cottbus.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.rz.tu-cottbus.de141.43.1.1AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE141.43.1.1
dns2.sbone.tu-cottbus.de141.43.99.10AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE141.43.99.10
math-s.math.tu-cottbus.de141.43.5.40AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE141.43.5.40

Checks

  • ✓ 4 nameservers #6
    Delegated to deneb.dfn.de, dns.rz.tu-cottbus.de, dns2.sbone.tu-cottbus.de, math-s.math.tu-cottbus.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: dns.rz.tu-cottbus.de, dns2.sbone.tu-cottbus.de, math-s.math.tu-cottbus.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 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): 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: dns.rz.tu-cottbus.de, dns2.sbone.tu-cottbus.de, math-s.math.tu-cottbus.de.
    #13

Nameservers

fail

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
dns.rz.tu-cottbus.de 141.43.1.1NOERROR, 24 ms, authoritativenono / yesrefused-
dns2.sbone.tu-cottbus.de 141.43.99.10NOERROR, 24 ms, authoritativenono / yesrefused-
math-s.math.tu-cottbus.de 141.43.5.40NOERROR, 24 ms, authoritativenono / 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.
  • i
    Identifying string disclosed
    These nameservers answer version queries with a string that is not a version number: deneb.dfn.de: "0".
    #17
  • ✓ Zone transfers refused #18
    No nameserver allows a zone transfer to the public.
  • ✗
    No DNS over TCP
    DNS over TCP is required (RFC 7766); without it, large answers such as DNSSEC responses fail. Not answering over TCP: dns.rz.tu-cottbus.de (141.43.1.1): dial tcp 141.43.1.1:53: i/o timeout; dns2.sbone.tu-cottbus.de (141.43.99.10): dial tcp 141.43.99.10:53: i/o timeout; math-s.math.tu-cottbus.de (141.43.5.40): dial tcp 141.43.5.40:53: i/o timeout.
    #19
  • ✓ EDNS supported #20
    All nameservers support EDNS(0).
  • ✓ Public addresses #21
    All nameserver addresses are publicly routable.

SOA

pass

serial 2026100701 · primary dns.rz.tu-cottbus.de

Found

Primary (MNAME)
dns.rz.tu-cottbus.de
Contact (RNAME)
hostmaster.tu-cottbus.de
Serial
2026100701
Refresh / retry
21600 s / 3600 s
Expire
1814400 s
Negative TTL
3600 s

Serial per nameserver

NameserverSerial
deneb.dfn.de (192.76.176.9)2026100701
deneb.dfn.de (2001:638:800:1::9)2026100701
dns.rz.tu-cottbus.de (141.43.1.1)2026100701
dns2.sbone.tu-cottbus.de (141.43.99.10)2026100701
math-s.math.tu-cottbus.de (141.43.5.40)2026100701

Checks

  • ✓ Serial 2026100701 everywhere #22
    All nameservers serve the same version of the zone.
  • ✓ Timers within recommendations #23
    SOA refresh 6h, retry 1h, expire 21d, negative TTL 1h.
  • ✓ Primary is a public nameserver #24
    The primary nameserver dns.rz.tu-cottbus.de is one of the listed nameservers.
  • ✓ Contact hostmaster@tu-cottbus.de #25
    The SOA RNAME hostmaster.tu-cottbus.de means hostmaster@tu-cottbus.de.
  • ✓ Date-based serial #26
    The serial 2026100701 follows the YYYYMMDDnn convention (2026-10-07).

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

11 records at the apex

Found

Read from
192.76.176.9:53
TypeValueTTL
SOAdns.rz.tu-cottbus.de. hostmaster.tu-cottbus.de. 2026100701 21600 3600 1814400 360086400
NSdns.rz.tu-cottbus.de.86400
NSmath-s.math.tu-cottbus.de.86400
NSdeneb.dfn.de.86400
NSdns2.sbone.tu-cottbus.de.86400
MX10 smtp-1.b-tu.de.86400
MX20 smtp-2.b-tu.de.86400
TXT"v=spf1 mx a:smtp-1.b-tu.de a:smtp-2.b-tu.de ?all"86400
CAA0 issue "harica.gr"86400
CAA0 issue "pki.dfn.de"86400
CAA0 iodef "mailto:btu-ca@b-tu.de"86400

Checks

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