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A: Classical DNS caching stores only the results of successful name resolutions. It is also possible for DNS servers to cache the results of unsuccessful name resolution attempts; this is called negative caching.
Q:What is the purpose of the "dig" command? Give an example of its use. A: "dig" is a DNS lookup utility. It is a flexible tool for interrogating DNS name servers. e.g. [root@localhost ~]# dig @192.168.2.16 ns.lux.on.ca ; <<>> DiG 9.5.0-P2 <<>> @192.168.2.16 ns.lux.on.ca ; (1 server found) ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57822 ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0 ;; WARNING: recursion requested but not available ;; QUESTION SECTION: ;ns.lux.on.ca. IN A ;; ANSWER SECTION: ns.lux.on.ca. 86400 IN A 142.204.141.75 ;; AUTHORITY SECTION: lux.on.ca. 86400 IN NS ns.lux.on.ca.lux.on.ca. ;; Query time: 9 msec ;; SERVER: 192.168.2.16#53(192.168.2.16) ;; WHEN: Sun Oct 26 23:34:19 2008 ;; MSG SIZE rcvd: 73
