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Security Zones

Firewall security zones divide a network into distinct segments—such as internal, external, and DMZ—each with its own rules and interface assignments. Zone-based firewalls extend this model by binding permissions to the zone itself rather than to individual interfaces.

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About this video

Firewall security zones provide a structured way to divide a network into distinct segments, each with its own trust level and access controls. Common zones include internal segments like management, operations, and sales, alongside an external or WAN-facing zone and a DMZ for publicly accessible resources. In simpler deployments, zones map directly to physical interfaces or VLAN sub-interfaces, meaning the number of zones equals the number of connections on the firewall. This interface-centric model is straightforward to understand and configure, but it ties policy directly to hardware, which can limit flexibility as networks grow. Zone-based firewalls offer a more scalable alternative by decoupling policy from individual interfaces. Instead of assigning rules to each interface separately, rules are defined at the zone level and interfaces are then assigned to a zone, inheriting its permissions automatically. This means multiple interfaces—for example, two separate internal network segments—can share a single zone policy, reducing administrative overhead and the risk of inconsistent rule sets. Understanding both models is essential for designing and managing firewall architectures that are both secure and adaptable to changing network requirements.

What you'll learn

Explain the concept of firewall security zones and distinguish between interface-based and zone-based firewall architectures

What's covered

Firewall Security Zones

Security Zone Concept
- Network Segmentation
- Zone Examples
  - Management Zone
  - Operations Zone
  - Sales Zone
- External vs Internal Zones
Interface-Based Zones
- Zones Per Interface
- Count Zones by Connections
Zone-Based Firewalls
- Permissions Assigned to Zone
- Interface Assigned to Zone
- Multiple Interfaces One Zone
- DMZ Zone

Key terms

Firewall: A network security device that monitors and controls incoming and outgoing traffic based on predefined security rules.
Network Segmentation: The practice of dividing a network into smaller segments to improve performance and limit the spread of security threats.
Demilitarized Zone: A network segment that sits between a trusted internal network and an untrusted external network, hosting public-facing services.
Virtual LAN: A logical grouping of network devices that behave as if they are on the same network regardless of physical location.
Security Zone: A logical grouping of network interfaces or segments within a firewall that share the same security policies and trust level.
Interface-Based Firewall: A firewall architecture where security policies are applied per physical interface, with each interface representing a distinct zone.
Zone-Based Firewall: A firewall architecture where interfaces are assigned to named zones, and security policies are applied to traffic flowing between zones rather than individual interfaces.

Topics

Firewalls Security Zones Dmz Zone Based Firewall Network Segmentation Network Security

Transcript

Security Zones

One of the concepts around firewalls is that we develop different zones, different security zones.

If we're splitting out our network into different segments, what we can do is start referring to these as zones, security zones. So we've got a security zone for management, we've got a security zone for operations, and a security zone for sales within the firewall. These would be individual interfaces, or sub interfaces if you're working with VLANs, but essentially what we're doing is the same exact thing. We have these different zones that we've broken these down into. One here is the external or WAN zone, and then we've got two internal zones here.

Many firewalls just base these security zones off of the interfaces. So we can count how many zones there are just by knowing there's one, two, three connections, and anything that's hanging off of each one of these is considered a zone.

Zone-Based Firewalls

But there are also some zone-based firewalls. With zone-based firewalls, instead we assign all the permissions to a zone, and then the interface gets assigned to that zone. So an interface gets assigned to a zone, and that zone has certain rules that are involved with it.

What that would look like is we would have a zone — maybe an external zone, which this interface gets assigned to — and then we have another zone, which is the internal, and then we have a DMZ. Let's say we wanted to add a whole other interface here, and this is another internal network right here. Then we could add it to the same zone as this internal, so now we add both those interfaces to that zone.

So that's just an example of a zone-based firewall.

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