You need to buy a new license to enable security
SL-29-SEC-K9 | Security License for Cisco 2901-2951 |
Four major technology licenses are available on the Cisco 2900 Series Integrated Services Routers; you can activate the licenses through the Cisco software activation process identified at
http://www.cisco.com/go/sa. The four licenses are as follows:
• IP Base: This technology package is available as default.
• Data
• Unified Communications
• Security (SEC) or Security with No Payload Encryption (SEC-NPE)
here is the link:
http://www.cisco.com/en/US/prod/collateral/routers/ps10537/data_sheet_c78_553896.html
HTH