Are RADIUS and TACACS+ Ever Allowed in FIPS 140-2 Compliant Scenarios? 

###RADIUS:
[Microsoft has FIPS-certified crypto modules for their recent operating systems](http://csrc.nist.gov/groups/STM/cmvp/documents/140-1/1401vend.htm) (search for "Microsoft").  

Enabling FIPS mode via Group Policy will force use of that crypto module.  However, as one answer pointed out, most RADIUS protocols are not allowable under FIPS.  PAP, CHAP, MS-CHAP, MS-CHAPv2 all use no/limited encryption or some form of MD hash (not allowed under FIPS).  There are some protocols that use FIPS-level encryption: EAP methods (PEAP, EAP-TLS).  

###TACACS+:
Cisco has taken their AAA servers through FIPS.  However, from the doc linked in one of the answers, it is only for 802.11i (wireless security using RADIUS), not for the TACACS+ piece.  

One issue with TACACS+ (which is hard to find) is that it apparently uses MD5 to protect TACACS+ traffic.  Search "TACACS+ MD5" and you should come up with a SANS Institute document that makes this statement.  Cisco does not say on its website what TACACS+ uses for encryption.  

Bottom line: TACACS+ in FIPS mode?  No, unless someone can show that the TACACS+ traffic is using 3DES or higher encryption.  RADIUS in FIPS mode? Yes, as long as you are using an EAP-method.