A network engineer is configuring a new Palo Alto Networks firewall that will operate in a network segment where both Layer 2 and Layer 3 traffic forwarding are required on the same physical interface. Specifically, the firewall needs to perform Layer 2 switching for some VLANs and Layer 3 routing for others, all through a single physical port. Which advanced interface configuration allows this mixed mode operation?
- AA physical interface configured as a Layer 2 interface with multiple VLANs assigned to it.
- BA physical interface configured as a 'VLAN interface' (Layer 3) with a 'Layer 2 subinterface' on it.
- CA physical interface configured as a Layer 3 interface with multiple Layer 3 subinterfaces.
- DA physical interface configured as a Virtual Wire, bridging Layer 2 segments.
Show answer & explanationAnswer & explanation
Correct answer: B. A physical interface configured as a 'VLAN interface' (Layer 3) with a 'Layer 2 subinterface' on it.
Palo Alto Networks firewalls can achieve mixed Layer 2 and Layer 3 operation on a single physical interface by configuring the physical interface as a Layer 2 interface, then creating Layer 3 VLAN interfaces (often called 'VLAN interfaces' or 'Layer 3 subinterfaces' in other contexts) on top of it. This allows the physical port to participate in Layer 2 switching for some VLANs while simultaneously routing for others via the VLAN interfaces.
Why the other options are wrong
- A. This allows Layer 2 switching for multiple VLANs but does not enable Layer 3 routing on the same physical port without additional configuration (like a VLAN interface).
- C. This allows multiple Layer 3 subinterfaces on a Layer 3 physical port, but the physical port itself does not perform Layer 2 switching.
- D. Virtual Wire interfaces are strictly Layer 2 and do not perform Layer 3 routing.
Mixed L2/L3 Interface
A configuration on a Palo Alto Networks firewall where a single physical interface simultaneously handles both Layer 2 switching and Layer 3 routing for different VLANs.
- Physical interface is configured as Layer 2.
- VLAN interfaces (Layer 3) are created on the Layer 2 physical interface.
- Enables flexible deployment in complex network segments.
Memory trick: To make one physical port 'speak' both L2 and L3, you teach the port L2, then give its VLANs their own L3 'voices'.