Hello,
Kindly follow the below mentioned steps in order to get internet working on windows end :
a) On windows side click on start - > control panel - > add/remove programs - > from here
remove the Parallels tools completely. Shut down Windows properly,restart the Mac.
b) After restarting Launch Parallels Desktop - > configure - > install Parallels Tools.
Now Parallels Tools will be automatically installed.
After installing Parallels Tools - :
1. Go to System Preferences - > Sharing - > Internet and turn off Apple Internet sharing.
2. Please set Parallels Network Adapter to Shared networking.
3. In Windows please open Network Connections -> right-click LAN icon -> find Local Area Connection properties ->
select Internet Protocol TCP/IP properties -> open General Tab and select Obtain IP and DNS server addresses
automatically check boxes.
Restart your Mac once and check for the internet connectivity on the windows end.