Domain report: ptb.de

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, ns1.ptb.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, ns1.ptb.de
NS in the zone: dns-1.dfn.de, dns-2.dfn.de, dns-3.dfn.de, ns1.ptb.de

Nameserver	Addresses	Network (AS)	Glue
dns-1.dfn.de	193.174.75.50 2001:638:d:b101::1	AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE	-
dns-2.dfn.de	193.174.75.54 2001:638:d:b102::1	AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE	-
dns-3.dfn.de	193.174.75.58 2001:638:d:b103::1	AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE	-
ns1.ptb.de	192.53.103.180 2001:638:610:bd02::14	AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE	192.53.103.180 2001:638:610:bd02::14

Checks

✓ 4 nameservers #6

Delegated to dns-1.dfn.de, dns-2.dfn.de, dns-3.dfn.de, ns1.ptb.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.ptb.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

Nameserver	Answer	Recursion	TCP / EDNS	AXFR	Version
dns-1.dfn.de 193.174.75.50	NOERROR, 13 ms, authoritative	no	yes / yes	refused	0
dns-1.dfn.de 2001:638:d:b101::1	NOERROR, 13 ms, authoritative	no	yes / yes	refused	0
dns-2.dfn.de 193.174.75.54	NOERROR, 7 ms, authoritative	no	yes / yes	refused	0
dns-2.dfn.de 2001:638:d:b102::1	NOERROR, 7 ms, authoritative	no	yes / yes	refused	0
dns-3.dfn.de 193.174.75.58	NOERROR, 8 ms, authoritative	no	yes / yes	refused	0
dns-3.dfn.de 2001:638:d:b103::1	NOERROR, 8 ms, authoritative	no	yes / yes	refused	0
ns1.ptb.de 192.53.103.180	NOERROR, 10 ms, authoritative	no	yes / yes	refused	9.11.22
ns1.ptb.de 2001:638:610:bd02::14	NOERROR, 10 ms, authoritative	no	yes / yes	refused	9.11.22

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: ns1.ptb.de: "9.11.22". 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 2026102041 · primary ns1.ptb.de

Found

Primary (MNAME): ns1.ptb.de
Contact (RNAME): postmaster.ptb.de
Serial: 2026102041
Refresh / retry: 1200 s / 3600 s
Expire: 604800 s
Negative TTL: 86400 s

Serial per nameserver

Nameserver	Serial
dns-1.dfn.de (193.174.75.50)	2026102041
dns-1.dfn.de (2001:638:d:b101::1)	2026102041
dns-2.dfn.de (193.174.75.54)	2026102041
dns-2.dfn.de (2001:638:d:b102::1)	2026102041
dns-3.dfn.de (193.174.75.58)	2026102041
dns-3.dfn.de (2001:638:d:b103::1)	2026102041
ns1.ptb.de (192.53.103.180)	2026102041
ns1.ptb.de (2001:638:610:bd02::14)	2026102041

Checks

✓ Serial 2026102041 everywhere #22

All nameservers serve the same version of the zone.
!

Unusual SOA timers

retry 1h should be shorter than refresh 20m. Current values: refresh 20m, retry 1h, expire 7d, negative TTL 1d.

#23
✓ Primary is a public nameserver #24

The primary nameserver ns1.ptb.de is one of the listed nameservers.
✓ Contact postmaster@ptb.de #25

The SOA RNAME postmaster.ptb.de means postmaster@ptb.de.
✓ Date-based serial #26

The serial 2026102041 follows the YYYYMMDDnn convention (2026-10-20).

DNSSEC

warn

Signed, DS published at parent

Found

Validated by resolver: yes
Denial of existence: NSEC
Signatures valid until: 26 October 2026

DS at the parent

Key tag	Algorithm	Digest	Matches a key
4561	RSASHA256 (8)	SHA256 79EC2508E9BDF233…	yes

DNSKEY in the zone

Key tag	Role	Algorithm
4561	KSK (257)	RSASHA256 (8)
7284	ZSK (256)	RSASHA256 (8)

Checks

✓ Signed and validated #27

The zone is signed, the parent publishes a DS record, and the resolver validates the answers.
✓ DS matches a key #28

The DS record at the parent matches a key in the zone: key tag 4561 (SHA256).
✓ Modern algorithms #29

Key algorithms: RSASHA256 (8).
!

Signatures expire soon

The earliest signature expires at 2026-10-26 01:16 UTC (in 97h0m0s). Check that automatic re-signing works.

#30
i

NSEC

The zone uses NSEC, so its full contents can be listed by walking the NSEC chain. That is fine unless the names are sensitive.

#31

Records

pass

16 records at the apex

Found

Read from: 193.174.75.50:53

Type	Value	TTL
SOA	ns1.ptb.de. postmaster.ptb.de. 2026102041 1200 3600 604800 86400	14400
NS	dns-3.dfn.de.	14400
NS	dns-1.dfn.de.	14400
NS	ns1.ptb.de.	14400
NS	dns-2.dfn.de.	14400
A	192.53.103.121	14400
AAAA	2001:638:610:bd01::121	14400
MX	10 mx1.bs.ptb.de.	14400
MX	20 mx1.berlin.ptb.de.	14400
TXT	"MS=ms58576303" "3600"	14400
TXT	"apple-domain-verification=XrEPkGN8FLiu5cwG"	14400
TXT	"v=spf1 ip4:192.53.103.120/32 ip4:194.94.94.97/32 ip6:2001:638:610:bd01::120/128 ip6:2001:638:610:cdce::61/128 include:spf.smtp.net ~all"	14400
CAA	0 issue "letsencrypt.org"	14400
CAA	0 issue "pki.dfn.de"	14400
CAA	0 issue "sectigo.com"	14400
CAA	0 issue "harica.gr"	14400

Checks

✓ TTLs within range #32

TTLs: A 4h, AAAA 4h, MX 4h, NS 4h. The NS TTL at the parent is 1d and in the zone 4h; 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.
✓ CAA restricts issuance #35

Certificates may be issued by: letsencrypt.org, pki.dfn.de, sectigo.com, harica.gr.