Ordering Cisco ASR 1000 Series Router Feature Licenses
In order to turn on services on Cisco ASR 1000 Series Routers, software feature licenses are required, in addition to the appropriate Cisco IOS XE Software. Currently two types of feature licenses are available: right-to-use (RTU) licenses and number-of-session licenses. Certain services require only RTU license, whereas other services require both RTU license and number-of-session licenses. In the future Cisco will introduce additional feature licenses for other value-added services (for example, intrusion prevention, etc.)

Broadband service: The Cisco ASR 1000 Series Router broadband application requires a RTU license and one or more number-of-session licenses. Unlike on other Cisco products, enabling Intelligent Service Gateway (ISG) technology on Cisco ASR 1000 Series Routers only requires the RTU license (FLASR1-BB-RTU(=)). There is no separate ISG license required other than the broadband RTU license.
You can combine multiple session licenses for the session count desired; for example, you can purchase two 4,000-session licenses for 8,000 sessions, and you can combine a 16,000-session license with a 4,000-session license for 20,000 sessions. You must order a number-of-session license even if you plan to enable only one session.
Please note with ASR1000-RP1, the maximum number of sessions is 24,000. To support maximum 32,000 sessions, you will need to order ASR1000-RP2 and ASR1000-ESP20.