Manual Chapter : Using Variable Assign to populate gating criteria

Applies To:

  • BIG-IP APM

    21.0.0, 17.5.1, 17.5.0, 17.1.3, 17.1.2, 17.1.1, 17.1.0, 17.0.0, 16.1.6, 16.1.5, 16.1.4, 16.1.3, 16.1.2, 16.1.1, 16.1.0, 15.1.10, 15.1.9

back-action Overview: Configuring step-up authentication

Updated Date: 04/30/2026

Using Variable Assign to populate gating criteria

When you set subroutine gating criteria to the perflow.custom or perflow.scratchpad variable, you must configure Variable Assign to specify its value.

Important: Using Variable Assign to populate a perflow variable other than perflow.custom and perflow.scratchpad causes subroutine results to become unreliable.

  1. Open the per-request policy for editing.

  2. Click the name of the Variable Assign agent.

    A Properties screen opens.

  3. Click Add new entry, and in the new entry, click the change link.

    A popup screen opens with Custom Variable selected on the left and Custom Expression selected on the right.

  4. On the left, select Predefined Variables.

    Additional fields display.

  5. For Group, select Per-Request Variables.

  6. For Variable, select one of the following:

    • Custom - Populates the perflow.custom variable.
    • Scratchpad - Populates the perflow.scratchpad variable.

  7. On the right, retain Custom Expression and configure the expression to provide a value.

    The Custom Expression option provides the greatest flexibility; you can select any other option and configure it.

  8. Click Finished.

    The popup window closes.

  9. Click Save.

    The Properties screen closes.