ipconfig /flushdns can clear the cache;
ipconfig /displaydns can display the dns cache.
本机的hosts文件也会在/displaydns时显示.其实这个在ipconfig –help里面有显示，就是一直没注意@_@
/all Display full configuration information.
/release Release the IP address for the specified adapter.
/renew Renew the IP address for the specified adapter.
/flushdns Purges the DNS Resolver cache.
/registerdns Refreshes all DHCP leases and re-registers DNS names
/displaydns Display the contents of the DNS Resolver Cache.
/showclassid Displays all the dhcp class IDs allowed for adapter.
/setclassid Modifies the dhcp class id.