Use these commands to make sure the DNS server only resolves local names.
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PS C:\Windows\System32\WindowsPowerShell\v1.0> nslookup www.google.com 74.91.125.138
Server: UnKnown
Address: 74.91.125.138
*** UnKnown can't find www.google.com: Server failed
PS C:\Windows\System32\WindowsPowerShell\v1.0> nslookup swbfrontps2.master.gamespy.com 74.91.125.138
Server: UnKnown
Address: 74.91.125.138
Name: swbfrontps2.master.gamespy.com
Address: 162.248.92.172
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PS C:\Windows\System32\WindowsPowerShell\v1.0> nslookup www.google.com 74.91.125.138
Server: UnKnown
Address: 74.91.125.138
*** UnKnown can't find www.google.com: Server failed
PS C:\Windows\System32\WindowsPowerShell\v1.0> nslookup swbfrontps2.master.gamespy.com 74.91.125.138
Server: UnKnown
Address: 74.91.125.138
Name: swbfrontps2.master.gamespy.com
Address: 162.248.92.172