Palo Alto Networks Next-Generation Firewalls rely on the concept of security zones in order to apply security policies. This means that access lists (firewall rules) are applied to zones and not interfaces – this is similar to Cisco’s Zone-Based Firewall supported by IOS routers.
Palo Alto Networks Next-Generation Firewalls zones have no dependency on their physical location and they may reside in any location within the enterprise network. This is also illustrated in the network security diagram below:
Figure 1. Palo Alto Firewall Security Zones can contain networks in different locations
The above topology illustrated shows VLANs 10, 11 ,12 and 2 managed by a Cisco Catalyst 4507R+E Switch and are all part of OSPF Area 0 and visible as routes in the Palo Alto Firewall. A Layer 3 aggregated link has been created between the Palo Alto Firewall (Interface ae1 on each firewall) and the Cisco 4507R+E Switch (Port-Channel 1 & 2).
When aggregation interface ae1.2 on the Palo Alto Firewall is configured to be part of the DMZ Security Zone, all networks learnt by the OSPF routing protocol on interface ae1.2 will be part of the DMZ Security Zone.
Creating a Security Zone involves tasks such as naming the zone, assigning the interfaces to the new zone created and more. Palo Alto Networks Next-Generation Firewalls won’t process traffic from any interface unless they are part of a Security Zone.
The diagram below depicts the order in which packets are processed by the Palo Alto Firewall:
Figure 2. Initial Packet Processing – Flow Logic of Palo Alto Next-Generation Firewall
It is without doubt Zone based firewalls provide greater flexibility in security design and are also considered easier to administer and maintain especially in large scale network deployments.
Palo Alto Networks Next-Generation Firewalls have four main types of Zones namely as shown in the screenshot below:
- Tap Zone. Used in conjunction with SPAN/RSPAN to monitor traffic.
- Virtual Wire. Also known as Transparent Firewall.
- Layer 2. Used when switching between two or more networks.
- Layer 3. Used when routing between two or more networks. Interfaces must be assigned an IP address.