H12-711_V4.0 Exam Dumps : HCIA-Security V4.0 Exam

A packet filtering firewall mainly works by examining the header information of packets and making forwarding or blocking decisions based on predefined rules. Its inspection is primarily focused on the network layer , where it checks information such as the source IP address , destination IP address , protocol type, and related packet header fields. Because of this, the correct answer is Network layer .

Packet filtering firewalls can also use some transport-layer information such as TCP or UDP port numbers in practical policy matching, but their fundamental classification in traditional firewall technology is based on network-layer packet filtering rather than deep inspection of application content. They do not analyze user data in the same detailed way as application-layer gateways or next-generation firewalls.

The physical layer only deals with bit transmission and hardware signaling, so it is not the layer used for packet filtering decisions. The data link layer focuses on MAC addresses and frame transmission within a local segment, while the application layer deals with application protocols such as HTTP, FTP, and DNS. Therefore, for a packet filtering firewall, the correct layer checked is the Network layer .

Huawei firewalls support creating multiple sub-interfaces on a single physical interface such as GE0/0/1 so that one physical link can carry traffic for multiple VLANs. Each sub-interface is configured with an 802.1Q VLAN tag, which allows it to logically represent one VLAN or one Layer 3 gateway interface for that VLAN. This design is commonly used when the firewall connects to a switch through a trunk and needs to provide routing and security control for several VLANs simultaneously.

The statement is incorrect because sub-interfaces can be added to security zones. A security zone is a logical security domain used for policy enforcement, and Huawei firewalls allow both physical interfaces and logical interfaces (including VLAN sub-interfaces) to be assigned to zones. This is essential for implementing interzone security policies between VLANs. For example, if two VLANs are mapped to two different sub-interfaces, placing each sub-interface into a different zone allows the firewall to apply access control, inspection profiles, and NAT based on zone-to-zone rules. Therefore, the claim that sub-interfaces cannot be added to security zones is false.