---
title: Authentication Extensions
canonical: https://openvpn.net/as-docs/authentication-extensions/
product: Access Server Docs
---

# Authentication Extensions

These plugins expand how users verify their identity when connecting to Access Server. They allow you to add multi-factor authentication (MFA), challenge/response mechanisms, external identity providers, or custom authentication logic using post-authentication scripts. Use these options to strengthen login security or integrate Access Server with your existing authentication infrastructure.

## In this section:

- [Duo 2FA](https://openvpn.net/as-docs/duo-2fa.md)
- [LastPass 2FA](https://openvpn.net/as-docs/lastpass-2fa.md)
- [iVALT 2FA](https://openvpn.net/as-docs/ivalt-2fa.md)
- [Challenge/Response](https://openvpn.net/as-docs/challenge-response.md)
- [Custom Authentication System](https://openvpn.net/as-docs/custom-authentication-system.md)

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Prev: [Post-Auth Guide](https://openvpn.net/as-docs/post-authentication-script-reference.md)
Next: [Duo 2FA](https://openvpn.net/as-docs/duo-2fa.md)
Index: https://openvpn.net/as-docs/llms.txt