最近网络不稳定，上国外网站都上不去，一查是DNS的问题。所以找了一个解决方案：建议在可控的最上级路由器上进行配置，以便网内所有设备上网而不必单独设置DNS。
国内服务器：
1. OpenerDNS：
42.120.21.30
2. 114DNS：114.114.114.114 114.114.115.115
3. oneDNS：112.124.47.27
4. aliDNS：223.5.5.5 223.6.6.6
国际服务器：
1. Google DNS8.8.8.8 8.8.4.4
2.V2EX DNS：199.91.73.222 178.79.131.110
3. OpenDNS208.67.222.222 208.67.220.220
推荐方案：
主DNS：openerDNS42.120.21.30
备DNS：aliDNS223.5.5.5
主DNS方便我们访问Google各项服务，备DNS确保我们的高可用性。
附：上海电信对各DNS跟踪的结果：
（跳跃节点越少越好，节点间数值越小越好，各位可根据自己网络的实际情况选择质量好、速度快的DNS。）
:->tracert 42.120.21.30
Tracing route to 42.120.21.30 over a maximum of 30 hops
1 7 ms 8 ms 7 ms 124.74.56.69
2 9 ms 7 ms 11 ms ow4157.sta.net.cn [124.74.227.157]
3 8 ms 8 ms 8 ms 124.74.215.137
4 * 13 ms * 124.74.166.114
5 * * * Request timed out.
6 11 ms 10 ms 11 ms 101.95.211.122
7 14 ms 14 ms 15 ms 42.120.246.78
8 14 ms 15 ms 14 ms 42.120.244.182
9 15 ms 15 ms 15 ms 42.120.244.230
10 * * * Request timed out.
11 15 ms 15 ms 14 ms 42.120.21.30
Trace complete.
:->tracert 114.114.114.114
Tracing route to public1.114dns.com [114.114.114.114]
over a maximum of 30 hops:
1 8 ms 8 ms 8 ms 124.74.56.69
2 11 ms 7 ms 7 ms ow4157.sta.net.cn [124.74.227.157]
3 8 ms 8 ms 8 ms 124.74.254.1
4 11 ms 11 ms 11 ms 202.101.63.210
5 15 ms 11 ms 11 ms 202.97.55.46
6 * * * Request timed out.
7 17 ms 16 ms 16 ms 58.213.224.170
8 14 ms 14 ms 14 ms public1.114dns.com [114.114.114.114]
Trace complete.
:->tracert 114.114.115.115
Tracing route to public2.114dns.com [114.114.115.115]
over a maximum of 30 hops:
1 8 ms 7 ms 7 ms 124.74.56.69
2 10 ms 11 ms 7 ms ow4149.sta.net.cn [124.74.227.149]
3 13 ms 11 ms 11 ms 124.74.215.41
4 10 ms 11 ms 11 ms 202.101.63.126
5 12 ms 15 ms 15 ms 202.97.55.34
6 20 ms 19 ms 16 ms 218.2.182.74
7 16 ms 15 ms 16 ms 58.213.224.170
8 14 ms 14 ms 14 ms public2.114dns.com [114.114.115.115]
Trace complete.
:->tracert 112.124.47.27
Tracing route to 112.124.47.27 over a maximum of 30 hops
1 7 ms 14 ms 8 ms 124.74.56.69
2 9 ms 8 ms 8 ms ow4149.sta.net.cn [124.74.227.149]
3 12 ms 10 ms 11 ms 124.74.210.125
4 * 11 ms 9 ms 101.95.218.90
5 * * * Request timed out.
6 11 ms 11 ms 11 ms 101.95.211.118
7 17 ms 16 ms 16 ms 42.120.246.74
8 32 ms 17 ms 15 ms 42.120.244.174
9 17 ms 17 ms 17 ms 42.120.244.246
10 * * * Request timed out.
11 67 ms 15 ms 16 ms 112.124.47.27
Trace complete.
:->tracert 223.5.5.5
Tracing route to public1.alidns.com [223.5.5.5]
over a maximum of 30 hops:
1 9 ms 8 ms 8 ms 124.74.56.69
2 8 ms 11 ms 12 ms ow4149.sta.net.cn [124.74.227.149]
3 26 ms 18 ms 15 ms 124.74.215.233
4 * 12 ms * 101.95.218.182
5 * * * Request timed out.
6 10 ms 11 ms 11 ms 101.95.211.118
7 15 ms 16 ms 16 ms 42.120.246.74
8 15 ms 15 ms 15 ms 42.120.244.174
9 16 ms 15 ms 15 ms 42.120.244.238
10 * * * Request timed out.
11 14 ms 15 ms 15 ms public1.alidns.com [223.5.5.5]
Trace complete.
:->tracert 223.6.6.6
Tracing route to public2.alidns.com [223.6.6.6]
over a maximum of 30 hops:
1 7 ms 8 ms 7 ms 124.74.56.69
2 10 ms 7 ms 8 ms ow4157.sta.net.cn [124.74.227.157]
3 11 ms 13 ms 9 ms 124.74.210.101
4 * * * Request timed out.
5 * * * Request timed out.
6 12 ms 11 ms 11 ms 101.95.211.126
7 15 ms 17 ms 16 ms 42.120.246.78
8 15 ms 15 ms 15 ms 42.120.244.198
9 17 ms 17 ms 16 ms 42.120.244.246
10 * * * Request timed out.
11 16 ms 16 ms 15 ms public2.alidns.com [223.6.6.6]
Trace complete.
:->tracert 8.8.8.8
Tracing route to google-public-dns-a.google.com [8.8.8.8]
over a maximum of 30 hops:
1 7 ms 8 ms 8 ms 124.74.56.69
2 11 ms 11 ms 7 ms ow4157.sta.net.cn [124.74.227.157]
3 12 ms 11 ms 11 ms 124.74.215.33
4 11 ms 11 ms 12 ms 61.152.86.174
5 10 ms 10 ms 10 ms 202.97.33.58
6 9 ms 9 ms 10 ms 202.97.33.2
7 40 ms 39 ms 40 ms 202.97.61.2
8 * 38 ms * 202.97.62.214
9 39 ms * 44 ms 209.85.241.58
10 * 64 ms * 209.85.241.99
11 * 67 ms * 209.85.243.23
12 * * * Request timed out.
13 * 64 ms * google-public-dns-a.google.com [8.8.8.8]
14 * 64 ms * google-public-dns-a.google.com [8.8.8.8]
15 * * * Request timed out.
16 * * * Request timed out.
17 63 ms * * google-public-dns-a.google.com [8.8.8.8]
18 * * * Request timed out.
19 * * 435 ms google-public-dns-a.google.com [8.8.8.8]
Trace complete.