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OpenVPN Cookbook - Second Edition by Jan Just Keijser

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Windows 8+ - ensuring DNS lookups are secure

Starting with Windows 8.1, Microsoft introduced a new feature for resolving hostnames to IP addresses. Whenever an application wants to resolve a hostname, a DNS query is sent out over all network adapters found in the system. The answer from the first adapter that responds to the query is used.

If a user wants to tunnel all traffic over a VPN in a secure manner, then this feature is not desirable. In a hostile network environment, a bogus IP address could be returned or even the fact that a DNS lookup for a particular host is made could be considered dangerous.

Starting with OpenVPN 2.3.10, a new option, block-outside-dns, was added to suppress this feature. In this recipe, we will show how to use this ...

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