DNS 反查；netlookup 應用

http://www.socialwork.com.hk/learn/dns/nslookup.html

http://bojack.pixnet.net/blog/post/3111052-nslookup-%E4%BD%BF%E7%94%A8%E6%96%B9%E6%B3%95

http://dns-learning.twnic.net.tw/bind/intro7.html

http://extra.pchome.com.tw/adm/faq_content02.htm?channel_no=&exh_no=P000007&pexh_no=P000181&cexh_no=H000185&faq_id=327&qnum=1