This chapter will focus on the following topics:
- – the role a firewall plays;
- – the types of firewalls:
- - NAT firewall,
- - packet-filtering firewall,
- - stateful firewall,
- - application firewall;
- – setting up a firewall;
- – different firewall strategies;
- – ACL-based firewalls:
- - IPv4 ACLs,
- - IPv6 ACLs;
- – zone-based firewalls:
- - the types of security zones in a network,
- - rules applied to inter-zone traffic,
- - configuring a ZFW.
5.1. Introducing firewalls
A firewall is a software or hardware system put in place between a reliable network and an unreliable one. The main purpose of putting in place a firewall is to filter out and prevent unwanted traffic from crossing the firewall barrier. In order to do this, a firewall must comply with the following recommendations:
- – it must be resistant to attacks;
- – it must be the only transit point between two networks;
- – it must ensure that the organization’s access control strategy is applied.
5.2. Types of firewalls
There are different kinds of firewalls. Some of these are:
- – NAT firewall: this hides a private IP address by translating it into a public IP address;
- – packet-filtering firewall: this makes it possible to filter packets from Layers 3 or 4 of the OSI model. This kind of firewall is simple to configure but is also vulnerable to identity-theft attacks;
- – stateful firewall: this carries out the same function as a packet-filtering firewall and also keeps track of the state of network connections (i.e. ...
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