The three-homed firewall is a firewall that is connected to three networks and controls which traffic is allowed to pass to ea of them. With this firewall type, one network connection is made to the Internet. The second network, sometimes known as perimeter network, connection is made to a network that contains resources that can be accessed by users on the Internet You will usually find web servers on this network. The third network connection is to the internal network. The firewall shoul not allow users on the Internet to access resources within the internal network, but it should allow resources within the perimeter network to access resources within the internal network. Figure 9.6 is an example of the three-homed firewall.
As with the bastion host, the cost of the three-homed firewall is usually one of the more inexpensive options, but you give u some of your security in using this option. If the firewall is breached, an attacker could gain access to the internal network.
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