Thanks Alan.
Would please answer another question in-line below.

Alan DeKok wrote:
Srinivasa Rao Chigurupati <srinivasarao@multitech.co.in> wrote:
  
1. Will FreeRadius challenges with access-challenge if auth-type is PAP?
    

  No.  Read the RFC's for how PAP works.

  
2.  How  FreeRadius  understands  incoming Radius access-request packet 
    contains PAP authentication information, CHAP authentication information
    or MS-CHAP authentication information or other authentication 
information?
    

  It looks in the packets.
I think if access-request packet contains user-password attribute, FreeRadius authenticates with PAP.
If access-request packet contains chap-password attribute, FreeRadius authenticates with CHAP.
Am I correct?
How MS-CHAP and other authentication methods are identified from access-request by FreeRadius?

  Alan DeKok.
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-- 
Thanks & Regards
Srinivasa Rao Chigurupati