Firewall Category 3

Divided from the firewall structure, the firewall mainly includes: single host firewall, router integrated firewall and distributed firewall.

A single host firewall is the most traditional firewall, independent of other network devices, and it is located at the network boundary.

This kind of firewall is actually similar to a computer architecture (as shown in the figure below). It also includes basic components such as CPU, memory, hard disk, etc. Of course, the motherboard can't be less, and there are also North and South Bridge chips on the motherboard. The main difference between it and the general computer is that the general firewall integrates more than two Ethernet cards because it needs to connect more than one internal and external network. The hard disk is used to store the basic programs used by the firewall, such as packet filtering programs and proxy server programs. Some firewalls also record the log records on this hard disk. Nevertheless, we cannot say that it is just like our usual PC. Because of the nature of its work, it determines that it must have very high stability, practicality, and very high system throughput. Because of this, it looks like the configuration similar to the PC, the price is far away.

With the development of firewall technology and the increasing application requirements, many firewalls have changed as a single host. The most obvious change is that now many middle and high-end routers have integrated firewall functions, and other firewalls are no longer an independent hardware entity, but a system composed of multiple software and hardware. "Distributed firewall."

The original single-host firewall was very expensive, and only a few large enterprises could afford it. In order to reduce corporate network investment, many middle-to-high-end routers now integrate firewall functions. Such as the Cisco IOS Firewall series. However, this kind of firewall is usually a lower-level packet filter type. This eliminates the need for companies to purchase routers and firewalls at the same time, which greatly reduces the cost of network equipment purchases.

Distributed firewalls are no longer just at the network boundary, but permeate every host on the network, protecting the entire internal network host. In the network server, a firewall system management software is usually installed, and a PCI firewall card with an integrated network card function is installed on the server and each host. Such a firewall card also has the dual functions of a network card and a firewall. Such a firewall system can completely protect the internal network. Each host considers the communication connection sent by any other host to be "untrusted" and requires strict filtering. Instead of the traditional boundary firewall, only the communication requests from external networks are "distrusted."