win 7上，用了 runas /user:administrator 启动命令行
输入 ipconfig /flushdns ，然后 /displaydns看见下面的。由于字数限制，下面只是一部分。
为啥还有残留？怎么彻底清除？
Windows IP Configuration
dl-client958.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client958.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 50.16.187.233
dl-client958.dropbox.com ----------------------------------------
No records of type AAAA
158.225.21.23.in-addr.arpa ----------------------------------------
Record Name . . . . . :
158.225.21.23.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-client939.dropbox.com dl-client934.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client934.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.206.222
dl-client934.dropbox.com ----------------------------------------
No records of type AAAA
dl-client926.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client926.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.44.36
dl-client926.dropbox.com ----------------------------------------
No records of type AAAA
dl-client910.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client910.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.82.212
dl-client910.dropbox.com ----------------------------------------
No records of type AAAA
dl-client902.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client902.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.208.17
dl-client902.dropbox.com ----------------------------------------
No records of type AAAA
dl-client878.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client878.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.207.120
dl-client878.dropbox.com ----------------------------------------
No records of type AAAA
dl-client830.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client830.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.245.131
dl-client830.dropbox.com ----------------------------------------
No records of type AAAA
dl-client822.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client822.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.190.242
dl-client822.dropbox.com ----------------------------------------
No records of type AAAA
dl-client814.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client814.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.23.107.172
dl-client814.dropbox.com ----------------------------------------
No records of type AAAA
dl-client806.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client806.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.23.107.117
dl-client806.dropbox.com ----------------------------------------
No records of type AAAA
48.130.101.75.in-addr.arpa ----------------------------------------
Record Name . . . . . :
48.130.101.75.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-client642.dropbox.com 32.214.17.50.in-addr.arpa ----------------------------------------
Record Name . . . . . :
32.214.17.50.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-client250.dropbox.com Record Name . . . . . :
12.166.160.108.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
client37.dropbox.com Record Name . . . . . :
12.166.160.108.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
client68.dropbox.com 202.111.23.23.in-addr.arpa ----------------------------------------
Record Name . . . . . :
202.111.23.23.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-client914.dropbox.com 53.169.21.23.in-addr.arpa ----------------------------------------
Record Name . . . . . :
53.169.21.23.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-client846.dropbox.com 28.124.23.23.in-addr.arpa ----------------------------------------
Record Name . . . . . :
28.124.23.23.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-client629.dropbox.com 76.217.129.174.in-addr.arpa ----------------------------------------
Record Name . . . . . :
76.217.129.174.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-client189.dropbox.com 80.208.16.50.in-addr.arpa ----------------------------------------
Record Name . . . . . :
80.208.16.50.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-client95.dropbox.com dl-debug36.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-debug36.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 107.20.249.207
dl-debug36.dropbox.com ----------------------------------------
No records of type AAAA
148.249.20.107.in-addr.arpa ----------------------------------------
Record Name . . . . . :
148.249.20.107.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-debug27.dropbox.com dl-debug24.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-debug24.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 107.20.249.119
dl-debug24.dropbox.com ----------------------------------------
No records of type AAAA
dl-debug12.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-debug12.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 107.20.249.56
dl-debug12.dropbox.com ----------------------------------------
No records of type AAAA
dl-client775.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client775.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 107.22.234.83
dl-client775.dropbox.com ----------------------------------------
No records of type AAAA
dl-client767.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client767.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 174.129.193.117
dl-client767.dropbox.com ----------------------------------------
No records of type AAAA
dl-client751.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client751.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 107.22.238.106
dl-client751.dropbox.com ----------------------------------------
No records of type AAAA
dl-client743.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client743.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 50.17.226.173
dl-client743.dropbox.com ----------------------------------------
No records of type AAAA
dl-client719.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client719.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 107.21.116.50
dl-client719.dropbox.com ----------------------------------------
No records of type AAAA
dl-client671.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client671.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 50.17.217.94
dl-client671.dropbox.com ----------------------------------------
No records of type AAAA
dl-client663.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client663.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 50.16.231.91
dl-client663.dropbox.com ----------------------------------------
No records of type AAAA
dl-client655.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client655.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 107.21.108.33
dl-client655.dropbox.com ----------------------------------------
No records of type AAAA
dl-client647.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client647.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.48.22
dl-client647.dropbox.com ----------------------------------------
No records of type AAAA
dl-client639.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client639.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.175.206
dl-client639.dropbox.com ----------------------------------------
No records of type AAAA
dl-client559.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client559.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.23.226.202
dl-client559.dropbox.com ----------------------------------------
No records of type AAAA
dl-client535.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client535.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.23.223.77
dl-client535.dropbox.com ----------------------------------------
No records of type AAAA
138.222.23.23.in-addr.arpa ----------------------------------------
Record Name . . . . . :
138.222.23.23.in-addr.arpa.
Record Type . . . . . : 12
Time To Live . . . . : 86400
Data Length . . . . . : 8
Section . . . . . . . : Answer
PTR Record . . . . . :
dl-client528.dropbox.com dl-client527.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client527.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.23.223.48
dl-client527.dropbox.com ----------------------------------------
No records of type AAAA
dl-client511.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client511.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.23.217.150
dl-client511.dropbox.com ----------------------------------------
No records of type AAAA
dl-client503.dropbox.com ----------------------------------------
Record Name . . . . . :
dl-client503.dropbox.com Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 23.21.220.167
dl-client503.dropbox.com ----------------------------------------
No records of type AAAA