I checked the following documentation http://technet.microsoft.com/en-us/library/hh831683.aspx, where said that is impossible to configure failover cluster on NAP. So, Is there a way to provide redundancy on NAP server?
To provide redundancy for a NAP enforcement server, client computers must be able to request and receive network access from multiple enforcement servers. Enforcement server redundancy is configured differently for each enforcement method. For more information,
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