In a layered defense strategy, firewalls provide perimeter security for the entire network and for internal network segments in the core. They can be used on separate VLAN segments. They can be used to separate the internal networks, separating one segment from the rest of the segments:
Several firewalls are used with several layers incorporated in them. Let's understand this process.
When the traffic flows in from an untrusted network, it encounters packet filter on the external router. In the next phase, the traffic steps into either a screened host firewall or a bastion host system. Then this system checks whether there are any suspicious packets, if yes, then it would get discarded. If the packet is not rejected then it would go to the interior screening router. After crossing all these checks, the packet travels to the final destination...
