Report for kernel-error.de

OK. Parent name servers are offering glue for domain's name servers. We received name servers list and it's IP addresses from parent name server (a.nic.de.).

OK. Found A records for all name servers.

• ns1.kernel-error.de. → 93.177.67.26
• ns2.kernel-error.org. → 148.251.30.203

To reach your name servers via IPv4 an A record is needed for each name server.

OK. Found AAAA records for all name servers.

• ns1.kernel-error.de. → 2a03:4000:38:20e::53
• ns2.kernel-error.org. → 2a01:4f8:262:4716::53

To reach your name servers via IPv6 an AAAA record is needed for each name server.

OK. All your name servers responded. We queried domain's records from all of your name servers and we received them successfully.

OK. No differences found. The glue provided by the parent name servers has to match the data provided by the authoritative name servers.

OK. Domain name servers are not allowing recursive queries. On all name servers which acts as caching name servers recursive queries should be restricted to local networks. Having open DNS servers can lead to abuses such as cache poisoning and DOS (denial of service) attacks. Cache poisoning attacks allows under certain conditions to redirect legitimate web traffic, email and other traffic to malicious hosts compromising security.

OK. Domain has 2 name servers. Recommended number, between 2 and 7 name servers (RFC 2182 recommends to have at least 3 authoritative name servers for domains).

OK. All your name servers reported identical NS records. Each name server should return identical NS records.

OK. No lame name servers found. All of your name servers are configured to be either master or slave for your domain.

OK. No private IPs found. Name servers using private IPs can't be reached from the Internet causing DNS delays.

OK. Found A records for each name servers.

• ns1.kernel-error.de. → 93.177.67.26
• ns2.kernel-error.org. → 148.251.30.203

To reach your name servers via IPv4 an A record is needed for each name server.

OK. Found AAAA records for all name servers.

• ns1.kernel-error.de. → 2a03:4000:38:20e::53
• ns2.kernel-error.org. → 2a01:4f8:262:4716::53

To reach your name servers via IPv6 an AAAA record is needed for each name server.

OK. All names are valid. Name server name should be a valid host name, no partial name or IP address.

OK. No stealth name servers found. All name servers returned by domain name servers should be listed at parent servers.

OK. No missing name servers found. All name servers returned by the parent name servers should have an NS record at your name servers.

OK. No CNAMEs found in NS records. RFC 2181, section 10.3 says that host name must map directly to one or more address record (A or AAAA) and must not point to any CNAME records. RFC 1034, section 3.6.2 says if a name appears in the right-hand side of RR (Resource Record) it should not appear in the left-hand name of CNAME RR, thus CNAME records should not be used with NS and MX records. Despite this restrictions, there are many working configuration using CNAME with NS and MX records.

OK. All name servers are allowing TCP connections. When response to a DNS query exceeds 512 bytes, TCP is negotiated and used, all name servers should allow TCP connections (port 53).

OK. Name servers are dispersed on 2 different C class networks:

• 148.251.30.0/24:
  • ns2.kernel-error.org.
• 93.177.67.0/24:
  • ns1.kernel-error.de.

Name servers should be dispersed (topologically and geographically) across the Internet to avoid risk of single point of failure (RFC 2182).

OK. Name servers are dispersed on 2 different Autonomous Systems:

• AS24940:
  • ns2.kernel-error.org.
• AS197540:
  • ns1.kernel-error.de.

Name servers should be dispersed (topologically and geographically) across the Internet to avoid risk of single point of failure (RFC 2182).

OK. Name servers software versions are not exposed:

• 148.251.30.203: "He's Dead, Jim!"
• 2a01:4f8:262:4716::53: "He's Dead, Jim!"
• 2a03:4000:38:20e::53: "He's Dead, Jim!"
• 93.177.67.26: "He's Dead, Jim!"

Exposing name server's versions may be risky, when a new vulnerability is found your name servers may be automatically exploited by script kiddies until you patch the system. Learn how to hide version.

OK. All name servers (2) have the same serial number [2024033135]. Having different serials on your name servers may show inconsistencies between name servers configuration (multiple masters), or communication errors (ACL and firewall issues).

OK. Serial number format OK [2024033135]. Your serial number is following general convention for serial number YYYYMMDDnn, where YYYY is four-digit year number, MM is the month, DD is the day and nn is the sequence number in case zone file is updated more than once per day.

OK. Primary name server is ns1.kernel-error.de. and is listed at the parent name servers. The MNAME field defines the Primary Master name server for the zone, this name server should be found in your NS records.

OK. Contact email for DNS problems is [email protected]. (root.kernel-error.de.). RNAME field defines an administrative email for your zone. RFC2142 recommends using hostmaster e-mail for this purpose, but any valid e-mail address can be used.

OK. Refresh interval is 14400. Recommended values [1200 .. 43200] (20 min ... 12 hours). Refresh field from SOA record determines how quickly zone changes are propagated from master to slave.

OK. Retry interval is 3600. Recommended values [120 .. 7200] (2 minutes .. 2 hours). Retry field from SOA record defines how often slave should retry contacting master if connection to master failed during refresh.

OK. Expire interval is 1209600. Recommended values [604800 .. 1209600] (1 week ... 2 weeks). Expiry defines zone expiration time in seconds after which slave must re-validate zone file, if contacting master fails then slave will stop responding to any queries.

OK. Minimum TTL value is 86400. Recommended values [3600 .. 86400] (1 hour ... 1 day). Minimum TTL was redefined in RFC 2308, now it defines the period of time used by slaves to cache negative responses.

OK. All name servers returned identical MX records.

OK. Found A records for all mail servers.

• smtp.kernel-error.de. → 148.251.30.205

To reach your mail servers via IPv4 an A record is needed for each mail server.

OK. Found AAAA records for all mail servers.

• smtp.kernel-error.de. → 2a01:4f8:262:4716::25

To reach your mail servers via IPv6 an AAAA record is needed for each mail server.

OK. All mail servers have reverse DNS entries configured correctly.

All mail servers should have a reverse DNS (PTR) entry for each IP address (RFC 1912). Missing reverse DNS entries will make many mail servers to reject your e-mails or mark them as SPAM.

All IP's reverse DNS entries should resolve back to IP address (IP → PTR → IP). Many mail servers are configured to reject e-mails from IPs with inconsistent reverse DNS configuration.

OK. No invalid characters found. Name field from MX records should be a valid host name.

OK. No private IPs found. Mail servers using private IPs can't be reached from the Internet causing mail delivery delays.

OK. No MX records duplicates (same IP addresses) found. Although technically valid, duplicate MX records have no benefits and can cause confusion.

OK. No IPs found in MX records. IP addresses are not allowed in MX records, only host names.

OK. No CNAMEs found in MX records. RFC 2181, section 10.3 says that host name must map directly to one or more address record (A or AAAA) and must not point to any CNAME records. RFC 1034, section 3.6.2 says if a name appears in the right-hand side of RR (Resource Record) it should not appear in the left-hand name of CNAME RR, thus CNAME records should not be used with NS and MX records. Despite this restrictions, there are many working configuration using CNAME with NS and MX records.

OK. Mail servers IPs are not blacklisted.

OK. Domain kernel-error.de. resolves to:

• 148.251.30.200

OK. No private IPs found for kernel-error.de.. Web servers using private IPs can't be reached from the Internet.

OK. Domain www.kernel-error.de. resolves to:

• 148.251.30.200

OK. No private IPs found for www.kernel-error.de.. Web servers using private IPs can't be reached from the Internet.