OSI model in relation with Firewalls - CompTIA Security +

10 Apr, 2025

Hola!

I found there is tons of points about firewalls for teh CompTIA Sec + Exam but they are everywhere!

╭( ๐_๐)╮ i mean they are not in order...

One of the recurring questions on the practice exams I'm taking focuses on this topic specifically. These notes help me visualize it better. I used Gemini to improve the visual formatting and also verified with its functionality that my references are accurate (study notes from the course I'm taking on Coursera).

There it goes;

• Network Switches:

  • Operate at Layer 2 (Data Link Layer).
  • Use MAC addresses for traffic switching via transparent bridging.

• Firewalls:

  • Operate at various OSI layers based on their type:
    • Packet Filtering Firewalls:
      • Operate at Layer 4 (Transport Layer).
      • Inspect packet headers for IP addresses and port numbers.
    • Stateful Firewalls:
      • Operate at Layer 4 (Transport Layer).
      • Track connections and allow return traffic for outbound requests.
    • Proxy Firewalls:
      • Operate at Layer 5 (Session Layer) and Layer 7 (Application Layer).
    • Layer 4 Firewalls:
      • Operate at Transport Layer.
      • Filter traffic based on port numbers and protocol data.
    • Layer 7 Firewalls:
      • Operate at Application Layer.
      • Inspect and control traffic based on data content and characteristics.