uni-mannheim.de

dns1.uni-mannheim.de, dns2.uni-mannheim.de, dns3.uni-mannheim.de

Found

Parent zone

de

Delegation from

a.nic.de (194.0.0.53)

NS at the parent

dns1.uni-mannheim.de, dns2.uni-mannheim.de, dns3.uni-mannheim.de

NS in the zone

dns1.uni-mannheim.de, dns2.uni-mannheim.de, dns3.uni-mannheim.de

Checks

• ✓ 3 nameservers #6

  Delegated to dns1.uni-mannheim.de, dns2.uni-mannheim.de, dns3.uni-mannheim.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: dns1.uni-mannheim.de, dns2.uni-mannheim.de, dns3.uni-mannheim.de.
• ✓ All names resolve #9

  Every nameserver name has an address and is not an alias.
• !

  Nameservers in one network

  all IPv4 addresses are in 134.155.96.0/24; all IPv6 addresses are in 2001:7c0:2900::/48. A single network failure takes all nameservers down; RFC 2182 recommends topologically separate networks (anycast setups are an exception).

  #10
• i

  All nameservers in one AS

  All nameserver addresses are announced by one network operator (AS553 (BELWUE - Universitaet Stuttgart, 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
• ✓ All reachable over IPv6 #13

  Every nameserver has an IPv6 address.

6 of 6 addresses answer authoritatively

Found

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.
• !

  Software version disclosed

  These nameservers report their software version via version.bind/version.server, which helps attackers find known vulnerabilities: dns1.uni-mannheim.de: "9.20.29-1~deb13u1-Debian"; dns2.uni-mannheim.de: "9.20.29-1~deb13u1-Debian"; dns3.uni-mannheim.de: "9.20.29-1~deb13u1-Debian". 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.

Signed, DS published at parent

Found

Validated by resolver

yes

Denial of existence

NSEC3

NSEC3

0 iterations, 8-byte salt

Signatures valid until

20 November 2026

DS at the parent

DNSKEY in the zone

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 19259 (SHA256).
• ✓ Modern algorithms #29

  Key algorithms: ECDSAP384SHA384 (14).
• ✓ Signatures valid until 2026-11-20 #30

  The earliest DNSKEY/SOA signature expires at 2026-11-20 16:00 UTC.
• !

  NSEC3 with extra iterations or salt

  NSEC3 uses 0 iterations and a 8-byte salt. RFC 9276 recommends 0 iterations and no salt: extra iterations cost resolvers CPU and add no real protection, and some validators treat high counts as insecure.

  #31