> Source: [sk163995](https://support.checkpoint.com/results/sk/sk163995)

# sk163995 - "Threat Prevention requires topology to be defined. At least one internal, one external and no undefined interfaces are required" warning when installing Threat Prevention policy in a VSX environment

| Property | Value |
|----------|-------|
| Solution ID | sk163995 |
| Date Created | 2019-12-15 |
| Last Modified | 2026-01-14 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20 |
| OS | Gaia |

## Symptoms

- In a Virtual System Extension (VSX) environment, the following warning appears during Threat Prevention policy installation, even though the policy installation completes successfully:

`Threat Prevention requires topology to be defined. At least one internal, one external and no undefined interfaces are required.`

## Cause

This warning is triggered when installing a Threat Prevention policy on a Virtual System (VS) that has one or more interfaces in an `Undefined` topology state.

A common scenario is a VS that includes a Warp Link (WRP) interface connected to a Virtual Switch or a Virtual Router. During the VS creation process, if **Calculate topology automatically** is enabled, such interfaces may remain in an `Undefined` state.

## Solution

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