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CISSP · Question #1477

Which of the following operates at the Network Layer of the Open System Interconnection (OSI) model?

The correct answer is A. Packet filtering. This question tests knowledge of which filtering/security mechanism operates at OSI Layer 3 (Network Layer). Packet filtering is the correct answer because it works based on IP addresses and network-level information.

Submitted by stefanr· Mar 5, 2026Communication and Network Security

Question

Which of the following operates at the Network Layer of the Open System Interconnection (OSI) model?

Options

  • APacket filtering
  • BPort services filtering
  • CContent filtering
  • DApplication access control

How the community answered

(49 responses)
  • A
    94% (46)
  • C
    2% (1)
  • D
    4% (2)

Why each option

This question tests knowledge of which filtering/security mechanism operates at OSI Layer 3 (Network Layer). Packet filtering is the correct answer because it works based on IP addresses and network-level information.

APacket filteringCorrect

Packet filtering operates at OSI Layer 3 (Network Layer) by inspecting and controlling traffic based on source/destination IP addresses, protocols, and sometimes ports defined in packet headers. This is the fundamental mechanism used by traditional router ACLs and basic firewalls that make forwarding/blocking decisions based on network-layer information. Because it examines IP header information - a Layer 3 construct - it is classified as a Network Layer operation.

BPort services filtering

Port services filtering operates at OSI Layer 4 (Transport Layer) because it inspects TCP/UDP port numbers, which are Transport Layer constructs, not Network Layer.

CContent filtering

Content filtering operates at OSI Layer 7 (Application Layer) because it must inspect the actual payload or data content of communications, which is only accessible at the Application Layer.

DApplication access control

Application access control operates at OSI Layer 7 (Application Layer) because it makes decisions based on application-specific data, user identity, and application behavior rather than network-level addressing.

Concept tested: OSI Layer 3 Network Layer security mechanisms

Source: https://learn.microsoft.com/en-us/azure/firewall/overview

Topics

#OSI model#Network layer#Packet filtering#Firewalls

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