Which of these tools can provide the most information about DNS queries?
A. dig
B. nslookup
C. host
D. named-checkconf
E. named-checkzone
題解
選項A，「dig」指令可以向網域名稱伺服器查詢詳細的網域名稱設定。如果查詢本站網域「magiclen.org」的話，會輸出：
| ; <<>> DiG 9.10.3-P4-Ubuntu <<>> magiclen.org | |
| ;; global options: +cmd | |
| ;; Got answer: | |
| ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43218 | |
| ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 | |
| ;; OPT PSEUDOSECTION: | |
| ; EDNS: version: 0, flags:; udp: 512 | |
| ;; QUESTION SECTION: | |
| ;magiclen.org. IN A | |
| ;; ANSWER SECTION: | |
| magiclen.org. 201 IN A 216.158.76.21 | |
| ;; Query time: 25 msec | |
| ;; SERVER: 127.0.1.1#53(127.0.1.1) | |
| ;; WHEN: Tue Nov 08 17:57:03 CST 2016 | |
| ;; MSG SIZE rcvd: 57 |
選項B，「nslookup」指令可以向網域名稱伺服器查詢網域名稱。如果查詢本站網域「magiclen.org」的話，會輸出：
| Server: 127.0.1.1 | |
| Address: 127.0.1.1#53 | |
| Non-authoritative answer: | |
| Name: magiclen.org | |
| Address: 216.158.76.21 |
選項C，「host」指令可以向網域名稱伺服器查詢網域名稱。如果查詢本站網域「magiclen.org」的話，會輸出：
| magiclen.org has address 216.158.76.21 | |
| magiclen.org mail is handled by 20 mx2.zoho.com. | |
| magiclen.org mail is handled by 10 mx.zoho.com. |
選項D，「named-checkconf」指令用來檢查「named」(DNS Server)設定檔案的語法正確性。
選項E，「named-checkzone」指令用來檢查「named」(DNS Server)的區域檔案(zone file)的正確性。
只有「dig」、「nslookup」、「host」是用來查詢網域名稱的資訊，其中又以「dig」所能提供的資訊最多，因此答案是選項A。