Set up outer firewall that perform DNAT and Masquerade.

I wasn't able to access the provided PDF file. However, I can still guide you through setting up an outer firewall that performs DNAT and masquerading. Here's a basic overview of the steps you need to follow:

1. Configure DNAT (Destination Network Address Translation):

   • Open your firewall configuration file (usually located in /etc/iptables/rules.v4 for iptables on Debian-based systems).
   • Add a rule to redirect incoming traffic on a specific port to the internal server IP address and port. For example:

     iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination 192.168.1.100:80

2. Configure Masquerading:

   • Enable masquerading to allow the internal server to respond to the incoming traffic. This is typically done in the POSTROUTING chain:

     iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

   • Save the iptables rules to ensure they persist after a reboot.

If you encounter specific issues or need detailed guidance, please provide more details or specific error messages you're facing, and I'll do my best to assist you further.