Cisco 3900 Router License - SL-39-SECNPE-K9 SEC No Payload Encryption License for Cisco 3900 Series  3925 3945 Routers.

2901 2911 2921 2951 Router
Cisco ISRs deliver innovative technologies running on the industry-leading Cisco IOS Software.
Cisco ISR G2 routers ship with a universal Cisco IOS Software image that contains all the features available for use on the routers. A specific feature set is activated by using technology package licenses such as Security, Unified Communications, and Data. Figure 1 shows the Cisco IOS Software packaging model for the Cisco 3900, 2900, and 1900 Series Integrated Services Routers.
 IOS Packaging Model for 3900, 2900 and 1900 Series Integrated Services Routers

Two types of universal images are supported on Cisco ISR G2 routers:
• Universal images with the universalk9 in the image name: This universal image offers all the Cisco IOS Software features, including strong payload cryptography features such as IP Security VPN (IPsec VPN), Secure Sockets Layer VPN (SSL VPN), and Secure Unified Communications.

• Universal images with the universalk9_npe in the image name: The strong control of encryption capabilities by Cisco Software Activation helps meet U.S. export control requirements for cryptography. However, some countries have import requirements that require that the platform does not support any strong payload cryptography. To satisfy the import requirements of those countries, Cisco allows you to order the router with an "npe" universal image that does not support any strong payload encryption. The npe image does support security features such as zone-based firewall and intrusion prevention through the SECNPE-K9 license.

For a given type and version of universal Cisco IOS Software image, both the Cisco 3945E and 3925 share the same Cisco IOS Software image; the Cisco 3945 and 3925 share another Cisco IOS Software image. Similarly, the Cisco 1921 and 1941 and Cisco 1941 Wireless routers share the same universal Cisco IOS Software image. Within the Cisco 2900 Series product family, the Cisco 2901, 2911, and 2921 share the universal Cisco IOS Software images for a given type and version. The Cisco 2951 has its own unique Cisco IOS Software image different from the rest of the Cisco 2900 Series images. Table 18 lists part numbers for universal Cisco IOS Software images for the Cisco 3900, 2900, and 1900 Series ISRs.