Dynamic Variables Overview
Variables constitute the dynamic component of a dynamic profile. You use variables in dynamic profiles as placeholders for dynamically obtained or dynamically generated information that the dynamic profiles use to configure subscriber interfaces.
How Dynamic Variables Work
Dynamic variables are data placeholders that you define and place in dynamic profiles. When a particular event occurs on an interface (for example, a DHCP client accesses the interface), the dynamic profiles obtain data to fill these placeholders from one of three possible sources—the interface receiving an incoming client data packet, an externally configured server (for example, RADIUS), or a value associated with each user-configurable variable.
For your convenience, Junos OS provides several predefined variables that you can use within a dynamic profile. Most of these variables relate to interface-specific data obtained directly from the interface that receives an incoming client data packets (for example, interface name, interface unit value, and so on). When a client accesses the interface, the router software extracts the necessary interface data, propagates this data to the dynamic profile, and then uses the dynamic profile to configure the interface for the accessing client.
You define user-defined variables for individual dynamic profiles at the [dynamic-profiles profile-name variables] hierarchy level. At this hierarchy level, you create an association between a variable value (for example, $junos-igmp-version) that appears in the body of the dynamic profile and data associated with that call value that is managed in an externally configured server (for example, a RADIUS VSA managed on a RADIUS server) or defined as a value in the variables stanza. When an event occurs on an interface to trigger the instantiation of a dynamic profile for the interface, the Junos OS obtains values for each variable from an external server (for example, from RADIUS authentication and authorization VSAs) during the subscriber authentication process. At run time, the variables are replaced by these actual values and are used to configure the subscriber interface.
Default Values for Predefined Variables
You can optionally configure default values for many of the predefined variables. If the external RADIUS server is not available or the VSA does not contain a value for the predefined variable, the Junos OS uses the default values.
When a default value is configured for a variable and RADIUS also returns a value, the system uses the value from RADIUS instead.
Related Topics
- Configuring a Basic Dynamic Profile
- Configuring a Dynamic Profile for Client Access
- Configuring a Dynamic Profile for Various Levels of Services
- Junos Predefined Variables
- User-Defined Variables
- Junos Predefined Variables That Correspond to RADIUS Attributes and VSAs
- Configuring Predefined Dynamic Variables in Dynamic Profiles
- Configuring User-Defined Dynamic Variables in Dynamic Profiles
- Dynamic Profiles Overview
- Subscriber Interface Overview
- Example: Firewall Dynamic Profile
- Example: IGMP Dynamic Profile
- RADIUS Attributes and Juniper Networks VSAs Supported by the AAA Service Framework
