PC use DNS google, client can't resolve domain name.

[oneaway]

Dear,
  My PC use DNS google is 8.8.8.8 so it can't access internet. I can't ping google.com but I can ping 8.8.8.8 is ok.
  I had create rule "Lan address" access  to any with any port. It's not ok.
  - A strange thing, when I use dns of AD internal address, the client access internet is ok. Thanks for any thing idea.