DNS Troubleshooting Facts

Question 1

ping

Answer 1

Contacts the DNS server to see if it responds. Be aware that the firewall protecting the DNS server may be configured to drop ICMP (ping) packets to prevent denial of service (DoS) attacks.

If the server doesn’t respond to the ping, it is not necessarily down.

Question 2

tracert or traceroute

Answer 2

Tests the route between a workstation and the DNS server.

Question 3

nslookup [host]

Answer 3

Queries the IP address of a host.

Question 4

nslookup

Answer 4

Starts nslookup in interactive mode. The default interactive mode query is for A records, but you can use the set type= command to change the query type.

Question 5

dig host name
host host name

Answer 5

Queries a host. The default query is for A records. You can change the default search by appending one of the following record types to the end of the command.
a—address records
any—any type of record
mx—mail exchange records
ns—name server records
soa—sort of authority records
hinfo—host info records
axfr—all records in the zone
txt—text records

Question 6

dig @IP address or host name domain

Answer 6

Queries the root server at the IP address or host name for the domain’s A records. You can change the default query type by appending a different record type to the end of the command.