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Please check this section periodically, as enhancements and new tools will be introduced regularly.
Introduction
HowIsMyDNS.com is a service that provides free online tools used to check and
validate your DNS data, to perform DNS and WHOIS lookups, and to make certain
IP calculations. The tests can only be performed on DNS zones visible to Internet;
private zones cannot be tested. Users do not have to install any software on their
workstations, a regular browser is enough; however, some functions require JavaScript
support. Each test is described below. If you have problems using the service,
contact help(at)howismydns(dot)com.
DNS Zone Report
Zone Test has been designed for analyzing your DNS Zone. A valid input for this
test is for example "howismydns.com".
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General Tests
This tool performs certain basic tests for the zone, including:
· Whether or not the target is a host (i.e. not NS or SOA record), only display
the A-record instead of performing a full test
· Existence of the zone
· NS records for the zone, A records for the NS records
· Current SOA
· A record of the zone if any
· Check that there are at least two authoritative nameservers for the zone
SOA Tests
· Display SOA Record, formatted and explained
· Serial number format check (low priority)
· NS agreement on SOA Serial #
· Check the nameserver's SOA-fields' serial are the same (see if the mname field differs from the others)
· SOA MNAME Check
· Check that MNAME is mentioned in NS records
NS Tests
NS Record tests verify that your NS record (Authoritative Name Server) information is the same
in all sources; Whois, DNS, and in servers themselves. Unmatched NS records are displayed in
"Warning" status. When a server does not answer with authority when it should, it's called a
Lame server. These servers are shown in the report also.
All servers are also tested using normal DNS Query to see if they provide a normal answer;
if they don't, it is usually caused by either a configuration problem or a firewall problem.
A-records for NS Servers are checked, warning is given if the IP addresses are private or
if the NS records are CNAMEs. Also reverse records for the NS records are tested; a warning
is issued if the PTRs resolve to multiple addresses or no addresses at all.
The parent zone may contain glue records for the NS records. This is usually necessary when
the NS records reside in the delegated zone; for example google.com NS records are ns1, ns2,
ns3 and ns4.google.com. This check requires a non-recursive search to be performed on the
parents' NS server.
NS records are also queries for their DNS server version identifier; this is informational
only and does not produce warnings.
The zone transfer enables the extraction of all DNS data available for the zone. According
to DNS best practices it is advisable to disable zone transfers for public slave zones.
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WHOIS Lookup
This tool performs a WHOIS Lookup using an external tool to verify zone status in registry.
Whois query can be performed for a DNS Zone or IP address/network. IP networks are resolved
from IP registry databases, DNS Zones from various Whois databases depending on the Top
level domain. The query resolves information about zone/IP contact information, name
servers, create/expiry dates, and current status.
DNS Lookup
This tool performs a basic forward DNS Lookup for all major RRs (A, AAAA, CNAME, MX, TXT,
SOA, SPF, SRV, NS, etc.) You can also query ANY record, which means that the tool will
resolve all types of Records found for this target.
Reverse DNS Lookup
This tool performs a basic reverse DNS lookup. It determines where the PTR record for
an ip-address is pointing to.
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