Hi Shuthakar,
Please find the required configuration for enabling tacacs+ in MDS 9500 Series...
aaa authenctication login default
aaa authentication login console
aaa accounting default
feature tacacs+
tacacs-server host 171.71.58.91
tacacs-server key <passkey>
tacacs-server timeout 30
Even you might need to set a VSA in Cisco ACS / TACACS server to succeed with the authentication.
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/mds9000/sw/4_1/configuration/guides/cli_4_1/clibook/cradtac1.html#wp1580356
Regards
Karthik