anchor.diff:  We can configure failover support for RADIUS server by creating additional
   RADIUS server entries per line of “/etc/raddb/server” file.
   
  -A) Test Setup:
  ---------------
  +==== Test Setup
   
   Our test environment is as follows:
   
  
positive.code: http://freeradius.org/download.html[FreeRADIUS]: Version 1.1.7 or later.
  Pam_Radius:: ftp://ftp.freeradius.org/pub/radius/pam_radius-1.3.17.tar.gz[Version 1.3.17].
  
  Configuration
  -------------
  There are two ways OpenVPN can be configured to support two factor authentication with YubiKey.
  
  A) OpenVPN Configuration without FreeRADIUS support:
  ----------------------------------------------------
  
  In this mode of configuration, OpenVPN server will be authenticating users
  by verifying username and user’s password against system password file 
  
negative.code: of Yubico PAM module for OpenVPN authentication.
  
  
  ====== Configuration of modified pam_yubico.so module at administrative level:
  
  Append the following line to the beginning of /etc/pam.d/radiusd file:
  
  