Palo Alto Networks Certified Network Security Engineer (PCNSE)Core ConceptsMedium
A large enterprise is deploying a Palo Alto Networks firewall in a data center to protect several internal server farms. The network design requires that the firewall inspect traffic between VLANs within the data center, and also provide secure access to these servers from external networks. Which interface type is most suitable for handling traffic between internal VLANs while maintaining security zones and applying policies?
- ATap interface
- BAggregate Ethernet interface
- CLayer 3 interface
- DVirtual wire (V-Wire) interface
Show answer & explanationAnswer & explanation
Correct answer: C. Layer 3 interface
A Layer 3 interface supports IP addressing, routing, and allows for the creation of subinterfaces to segment VLANs into separate security zones. This enables the firewall to act as a router between VLANs and enforce granular security policies.
Why the other options are wrong
- A. Tap interfaces are for passive monitoring only and do not participate in traffic forwarding or policy enforcement.
- B. Aggregate Ethernet interfaces bundle physical links for redundancy and bandwidth, but don't define the L3 routing function for VLANs.
- D. Virtual wire interfaces connect two ports transparently at Layer 2, primarily for inline deployment without changing network topology, not for routing between VLANs.
Layer 3 Interface
A firewall interface configured with an IP address, capable of routing traffic between different subnets and enforcing security policies based on zones.
- Has an IP address
- Participates in routing
- Supports subinterfaces for VLANs
- Enforces zone-based policies
Memory trick: Each firewall port plays a different role in the network's story.