1, how to query DNS resolution
Parse command: the ping; Host; DIG
2, dig named query parsing content
Which query the status points are:
NOERROR: mean no mistake;
NXDOMAIN: negative answer, this record does not exist;
REFUSED: the DNS server to deny access;
SERVFAIL: dns query failed record, dns can not reach higher deny local cache;
Mark is divided into:
QR Query query flag, representing the query operation
RD recursion Desired, on behalf of hope recursive query operation
RA recursion set the Available in return, on behalf of the query server supports recursive query operation
AA authoritative answer authoritative reply, if the query results are provided by the management domain name server rather than the cache server, called authoritative reply
Query types are divided into:
A record: the IPV4 address resolution;
AAA record: IPV6 address resolution;
NS Record: Record the domain name server;
MX records: mail exchange record;
PTR record (record pointer): Reverse Record A record, the role is to resolve IP addresses to domain names;
CNAME record: alias record;
3, common DNS resolution error analysis
(1) error message: Service unreachable (no server could be reched)
Cause: The service is open; firewall whether to allow; the port is turned on; the network is unobstructed;
Modify the error: open service that allows firewall, open ports, check the network between two hosts is smooth
(2) the error message: Service failed to restart
Cause: The view logs, error investigation
Modify Error: This is due to the generation of 52 lines of code error, you can modify
(3) error message: When a dig query, the status bar appears error message (REFUSED; SERVFAIL);
Cause: The configuration file does not allow caching and access;
Modify error: modify the configuration asked members
That is, when some of the above DIG query, appears wrong wrong, hope that helps.
