You're reading from OPNsense Beginner to Professional Protect networks and build next-generation firewalls easily with OPNsense

Product type Paperback

Published in Jun 2022

Publisher Packt

ISBN-13 9781801816878

Length 464 pages

Edition 1st Edition

Tools

FreeBSD

Concepts

Network Security

Author (1):

Julio Cesar Bueno de Camargo

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Table of Contents (25) Chapters

Preface

1. Section 1: Initial Configuration

2. Chapter 1: An OPNsense Overview FREE CHAPTER

3. Chapter 2: Installing OPNsense

4. Chapter 3: Configuring an OPNsense Network

5. Chapter 4: System Configuration

6. Section 2: Securing the Network

7. Chapter 5: Firewall

8. Chapter 6: Network Address Translation (NAT)

9. Chapter 7: Traffic Shaping

10. Chapter 8: Virtual Private Networking

11. Chapter 9: Multi-WAN – Failover and Load Balancing

12. Chapter 10: Reporting

13. Section 3: Going beyond the Firewall

14. Chapter 11: Deploying DHCP in OPNsense

15. Chapter 12: DNS Services

16. Chapter 13: Web Proxy

17. Chapter 14: Captive Portal

18. Chapter 15: Network Intrusion (Detection and Prevention) Systems

19. Chapter 16: Next-Generation Firewall with Zenarmor

20. Chapter 17: Firewall High Availability

21. Chapter 18: Website Protection with OPNsense

22. Chapter 19: Command-Line Interface

23. Chapter 20: API – Application Programming Interface

24. Other Books You May Enjoy

Outbound NAT

Back to our examples, as we discussed at the beginning of this chapter, let's use the example of a small company with 10 computers and just a single public IP address in its WAN connection. Moving on in this scenario, we have the goal to connect all those computers to the internet just using firewall capabilities. How do we achieve that? By creating an outbound NAT! Let's see how things work. The following is an example topology of outbound NAT traffic:

Figure 6.5 – Outbound NAT example

As we can see in the preceding figure, three clients are each accessing a website. Let's pick the host 192.168.10.11: it is accessing the https://cloudfence.eu website, but to the CloudFence web server, the source IP address is the public IP of OPNsense firewall 200.200.200.1 with source port 10200. So what is happening here? The outbound NAT rule is translating from the internal source IP to a public IP address, so from a TCP perspective...