Linux firewall entry: Network topology

Article title: Linux firewall entry: network topology. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.
The so-called network Topology refers to the network architecture, where routers are placed, where hosts are placed, hubs, and how route packets are arranged, after some planning, the network structure is displayed. To introduce a firewall system to an internal network, it is often necessary to change the network topology and select the most appropriate structure based on the features of the firewall and the benefits to be achieved. Therefore, changing the network topology is an inevitable result. you must be prepared first. After the psychological layer has been prepared, everything will naturally get up, not to worry about unnecessary fear.
The simplest firewall topology is the bastion firewall system. its structure is shown in:
Figure 1. Bastion firewall

The firewall host with two network cards is called dual-homed (two network interfaces) bastion firewall. In this study, we will use this simple topology to familiarize everyone with the basic firewall construction process.
Of course, there are still many changes in the firewall system. However, due to time factors, we cannot introduce them one by one in this study. Let's take a look at the network topology in the Middle School: (the figure is not shown in this handout in the classroom)