[These were obtained from d0.org.afilias-nst.org.]
Glue at parent nameservers
The parent servers are not providing glue for all your nameservers. This means that they are supplying the NS records (host.example.com), but not supplying the A records.
That may cause some extra milliseconds in DNS. This will usually occur if your DNS servers are not in the same TLD as your domain
Some servers does not provide A records for nameservers.
missing A record(s) for (ns1.crazydomains.com) at nameserver 188.8.131.52
missing A record(s) for (ns1.crazydomains.com) at nameserver 184.108.40.206
missing A record(s) for (ns1.crazydomains.com) at nameserver 220.127.116.11
Nameservers report identical NS records
The NS records at your nameservers are different
At (18.104.22.168 22.214.171.124 126.96.36.199) there are nameservers: nsbak.pavietnam.net. ns1.crazydomains.com. ns1.pavietnam.vn. ns2.pavietnam.vn.
At (188.8.131.52) there are nameservers:
All of your nameservers listed at the parent nameservers responded.
Nameserver name validity
All of the NS records that your nameservers report are valid (no IPs or partial domain names).
Number of nameservers
You have 4 nameservers. You must have at least 2 nameservers (RFC2182 section 5 recommends at least 3 nameservers), and preferably no more than 7.
Missing (stealth) nameservers
All your nameservers are also listed at the parent servers.
Root missing nameservers
All of the nameservers listed at the parent nameservers are also listed as NS records at your nameservers.
Nameservers on separate class C's
Nameservers are in a different networks.
All of your NS records appear to use public IPs.
SOA record is:
Some nameservers have a different soa serial number That can occur because of recent master update (slave have not loaded master zone yet) or the is a problem in DNS.
There is serial at nameserver(s) (184.108.40.206)
There is serial 2017111114 at nameserver(s) (220.127.116.11)
There is serial 2017112114 at nameserver(s) (18.104.22.168)
SOA (Start of Authority) record states that your master (primary) name server is: , but that server is not listed at the parent servers.
SOA serial number is: This not appears to be in the recommended format of YYYYMMDDnn, where 'nn' is the revision. This number must be incremented every time you make a DNS change.
SOA Retry interval is : seconds. This seems too small. (Values about 3600-7200 seconds is good if not using DNS NOTIFY; RFC1912 2.2 recommends a value between 1200 to 43200 seconds (20 minutes to 12 hours)). This value determines how often secondary/slave nameservers check with the master for updates.
SOA Retry interval is : seconds. This seems too small. (Values about 120-7200 seconds is good). The retry value is the amount of time your secondary/slave nameservers will wait to contact the master nameserver again if the last attempt failed.
SOA Expire time is : seconds. This seems too small. (Values 604800 to 2419200 seconds (1-4 weeks) is good). RFC1912 suggests 2-4 weeks. This is how long a secondary/slave nameserver will wait before considering its DNS data stale if it can't reach the primary nameserver.
SOA Expire time is : seconds. This seems too small. (about 300 to 86400 seconds or 5 min - 24 hours is good). RFC2308 suggests a value of 1-3 hours. This value used to determine the default (technically, minimum) TTL (time-to-live) for DNS entries, but now is used for negative caching.
Trace to phapthihoi.org
lookup phapthihoi.org at A.ROOT-SERVERS.NET(22.214.171.124) 10 ms
A.ROOT-SERVERS.NET(126.96.36.199) refer to a0.org.afilias-nst.info(188.8.131.52)
lookup phapthihoi.org at a0.org.afilias-nst.info(184.108.40.206) 160 ms
a0.org.afilias-nst.info(220.127.116.11) refer to ns1.pavietnam.vn(unknow IP)
extra IP lookup for ns1.pavietnam.vn at root server A.ROOT-SERVERS.NET(18.104.22.168)
lookup ns1.pavietnam.vn at A.ROOT-SERVERS.NET(22.214.171.124) 9 ms
A.ROOT-SERVERS.NET(126.96.36.199) refer to d.dns-servers.vn(188.8.131.52)
lookup ns1.pavietnam.vn at d.dns-servers.vn(184.108.40.206) 268 ms
d.dns-servers.vn(220.127.116.11) refer to ns2.pavietnam.vn(18.104.22.168)
lookup ns1.pavietnam.vn at ns2.pavietnam.vn(22.214.171.124) 301 ms
got A record 'ns1.pavietnam.vn IN A 126.96.36.199' from ns1.pavietnam.vn(188.8.131.52)
lookup phapthihoi.org at ns1.pavietnam.vn(184.108.40.206) 234 ms
got A record 'phapthihoi.org IN A 220.127.116.11' from phapthihoi.org(18.104.22.168)