「TWNIC警告：2/1使用Google等公共DNS建議改用101 預防連不上網」
https://ec.ltn.com.tw/article/breakingnews/2686668
新聞內容提到：
台灣網路資訊中心呼籲網路使用者，如2月1日當日發現網站無法連線時，應檢查電腦的DNS是否使用上述Google、IBM、Cloudflare等公共DNS，如果是，可將DNS更換為ISP所提供DNS之IP位址、或TWNIC之101.101.101.101，即可順利連線。
真的是這樣嗎？基於好奇，剛剛測試了一下，發現將DNS設定成101.101.101.101上網會卡住。後來進一步用dig指令測試，發現101.101.101.101服務根本時好時壞。
ok的時候查詢延遲21ms：
root@nacestudio-ThinkPad-T420s:/home/nacestudio# dig tw.yahoo.com @101.101.101.101; <> DiG 9.11.3-1ubuntu1.3-Ubuntu <> tw.yahoo.com @101.101.101.101
;; global options: +cmd
;; Got answer:
;; ->>HEADER<
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: e6e3a483ad021f58ae85f27c5c525f9066f2f9d23aa91939 (good)
;; QUESTION SECTION:
;tw.yahoo.com. IN A
;; ANSWER SECTION:
tw.yahoo.com. 60 IN CNAME atsv2-fp-shed.wg1.b.yahoo.com.
atsv2-fp-shed.wg1.b.yahoo.com. 22 IN A 124.108.103.104
atsv2-fp-shed.wg1.b.yahoo.com. 22 IN A 124.108.103.103
;; Query time: 21 msec
;; SERVER: 101.101.101.101#53(101.101.101.101)
;; WHEN: Thu Jan 31 10:38:08 CST 2019
;; MSG SIZE rcvd: 135
壞掉的時候查詢要3753ms (快四秒了，哇哩咧)，嚇暑輪！
root@nacestudio-ThinkPad-T420s:/home/nacestudio# dig tw.yahoo.com @101.101.101.101; <> DiG 9.11.3-1ubuntu1.3-Ubuntu <> tw.yahoo.com @101.101.101.101
;; global options: +cmd
;; Got answer:
;; ->>HEADER<
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 861c906af3e702cf21e64c845c52608da0dd251c1d6ab349 (good)
;; QUESTION SECTION:
;tw.yahoo.com. IN A
;; ANSWER SECTION:
tw.yahoo.com. 60 IN CNAME atsv2-fp-shed.wg1.b.yahoo.com.
atsv2-fp-shed.wg1.b.yahoo.com. 60 IN A 124.108.103.104
atsv2-fp-shed.wg1.b.yahoo.com. 60 IN A 124.108.103.103
;; Query time: 3753 msec
;; SERVER: 101.101.101.101#53(101.101.101.101)
;; WHEN: Thu Jan 31 10:42:21 CST 2019
;; MSG SIZE rcvd: 135
有時候甚至timeout不給回應了QQ，這樣是要怎麼上網啦!
root@nacestudio-ThinkPad-T420s:/home/nacestudio# dig tw.yahoo.com @101.101.101.101; <> DiG 9.11.3-1ubuntu1.3-Ubuntu <> tw.yahoo.com @101.101.101.101
;; global options: +cmd
;; connection timed out; no servers could be reached
Trace route了一下，哇賽，要74ms，而且經過好多節點：
root@nacestudio-ThinkPad-T420s:/home/nacestudio# traceroute 101.101.101.101 -U -p 53
traceroute to 101.101.101.101 (101.101.101.101), 30 hops max, 60 byte packets
1 h254.s98.ts.hinet.net (168.95.98.254) 13.975 ms 14.812 ms 14.801 ms
2 skc1-3315.hinet.net (168.95.32.6) 14.787 ms 14.775 ms 14.763 ms
3 skc1-3021.hinet.net (220.128.24.34) 19.213 ms skc1-3021.hinet.net (220.128.24.166) 19.550 ms skc1-3021.hinet.net (220.128.24.34) 19.231 ms
4 tpdb-3021.hinet.net (220.128.24.114) 18.619 ms tpdt-3022.hinet.net (220.128.25.10) 19.162 ms tpdb-3021.hinet.net (220.128.24.10) 18.861 ms
5 tpdt-3011.hinet.net (220.128.13.89) 23.090 ms tpdt-3012.hinet.net (220.128.14.89) 22.247 ms tpdt-3011.hinet.net (220.128.24.137) 23.060 ms
6 r4208-s2.hinet.net (220.128.3.173) 18.707 ms 18.487 ms 18.466 ms
7 203-75-228-249.HINET-IP.hinet.net (203.75.228.249) 20.148 ms 20.122 ms 19.098 ms
8 * * *
9 * * *
10 * * *
11 * * twnic-public-dns.twnic.tw (101.101.101.101) 74.117 ms
如果用hinet 168.95.1.1只要15ms就到了，兩者相差了60ms左右，而且才經過4個節點就到了，好近呀！
root@nacestudio-ThinkPad-T420s:/home/nacestudio# traceroute 168.95.1.1 -U -p 53
traceroute to 168.95.1.1 (168.95.1.1), 30 hops max, 60 byte packets1 h254.s98.ts.hinet.net (168.95.98.254) 14.083 ms 14.028 ms 14.006 ms
2 skc1-3315.hinet.net (168.95.32.6) 15.098 ms 15.075 ms 15.054 ms
3 220-128-32-197.HINET-IP.hinet.net (220.128.32.197) 15.024 ms 220-128-32-193.HINET-IP.hinet.net (220.128.32.193) 15.008 ms 14.988 ms
4 220-128-32-203.HINET-IP.hinet.net (220.128.32.203) 14.967 ms 14.939 ms 14.911 ms
root@nacestudio-ThinkPad-T420s:/home/nacestudio#
查詢時間也短，只要14ms：
root@nacestudio-ThinkPad-T420s:/home/nacestudio# dig tw.yahoo.com @168.95.1.1; <> DiG 9.11.3-1ubuntu1.3-Ubuntu <> tw.yahoo.com @168.95.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 3072
; COOKIE: 4dfdffff09c582bdb474093d5c525f86af6b91cdae5bc3bf (good)
;; QUESTION SECTION:
;tw.yahoo.com. IN A
;; ANSWER SECTION:
tw.yahoo.com. 40 IN CNAME atsv2-fp-shed.wg1.b.yahoo.com.
atsv2-fp-shed.wg1.b.yahoo.com. 46 IN A 124.108.103.103
atsv2-fp-shed.wg1.b.yahoo.com. 46 IN A 124.108.103.104
;; Query time: 14 msec
;; SERVER: 168.95.1.1#53(168.95.1.1)
;; WHEN: Thu Jan 31 10:37:58 CST 2019
;; MSG SIZE rcvd: 135
結論就是，現階段將DNS設成101.101.101.101會有很多不穩定的狀況，連線會有異常。
hinet user還是建議先用hinet DNS (168.95.1.1) 比較穩，提供給版上各位專家參考囉！
