Ports and protocol identifiers (protocol IDs) are not the same thing, though they are often confused. If you’re planning to take the Security+ exam, you should have a basic understanding of all relevant protocols and ports and know the difference between a port and a protocol ID.
For example, can you answer this question?
Q. You need to enable the use of NetBIOS through a firewall. Which ports should you open?
A. 137 through 139
B. 20 and 21
C. 80 and 443
D. 22 and 3389
More, do you know why the correct answer is correct and the incorrect answers are incorrect? The answer and explanation is available at the end of this post.
Protocol IDs and Ports
Ports and protocol identifiers (protocol IDs) are not the same thing, though they are often confused. Well-known ports identify many services or protocols.
However, many protocols aren’t identified by the port, but instead by the protocol ID. For example, within IPsec, protocol ID 50 indicates the packet is an Encapsulating Security Payload (ESP) packet, and protocol ID 51 indicates it’s an Authentication Header (AH) packet. Similarly, ICMP has a protocol ID of 1, TCP is 6, and UDP is 17.
You can use a protocol ID to block or allow traffic on routers and firewalls just as you can block or allow traffic based on the port. Note that it isn’t accurate to say that you can allow IPsec ESP traffic by opening port 50. IANA lists port 50 as a Remote Mail Checking Protocol. However, you can allow IPsec traffic by allowing traffic using protocol ID 50.
Protocol analyzers can capture and examine IP headers to determine the protocol ID and the port, as well as read any unencrypted data.
The 601 Version of the Study Guide
The CompTIA Security+: Get Certified Get Ahead: SY0-601 Study GuideEach of the eleven chapters presents topics in an easy to understand manner and includes real-world examples of security principles in action.
You’ll understand the important and relevant security topics for the Security+ exam, without being overloaded with unnecessary details. Additionally, each chapter includes a comprehensive review section to help you focus on what’s important.
Over 300 realistic practice test questions with in-depth explanations will help you test your comprehension and readiness for the exam. The book includes:
- A 75 question pre-test
- A 75 question post-test
- Practice test questions at the end of every chapter.
Each practice test question includes a detailed explanation to help you understand the content and the reasoning behind the question. You’ll be ready to take and pass the exam the first time you take it.
If you plan to pursue any of the advanced security certifications, this guide will also help you lay a solid foundation of security knowledge. Learn this material, and you’ll be a step ahead for other exams. This SY0-601 study guide is for any IT or security professional interested in advancing in their field, and a must-read for anyone striving to master the basics of IT security.
Memorize These Ports
There are 1,024 well-known ports, but you don’t need to know them all. However, at a minimum, you should know the ports listed in the table. It lists all of the ports specifically mentioned in the CompTIA objectives along with several others you should know when preparing for the exam. Some of these ports are outside the well-known ports range. However, you can use this table as a single source to memorize all of the relevant ports.
Some commonly used well-known ports
Some topics just require you to memorize information, and port numbers is one of those topics. It’s worth your time to memorize these port numbers and their related protocol. Don’t be surprised if you see questions such as “What is the default port for _______?” If you have the table memorized, these questions will be trivial to you.
You also need to know these ports for advanced questions, such as configuring a firewall rule to allow or block traffic based on the protocol.
When you take the CompTIA Security+ exam, you can write down your own notes as soon as you start. Many successful test takers memorize the ports in this table and write down the table as their very first action when they start the exam. Later, when they come across a question that requires the knowledge of a port number, it’s as simple as looking at their notes. If you don’t know these ports now, practice writing this table from memory so you’re ready when it’s time for the live exam.
Remember this
Administrators use ports to identify traffic they want to allow or block. For example, SSH, SCP, and SFTP use TCP port 22 by default. So, by configuring a firewall to allow traffic on port 22, they are allowing SSH, SCP, and SFTP traffic. Memorize the ports in the table so that you can answer CompTIA Security+ port-related questions very easily.
Q. You need to enable the use of NetBIOS through a firewall. Which ports should you open?
A. 137 through 139
B. 20 and 21
C. 80 and 443
D. 22 and 3389
Answer is A. Network Basic Input/Output System (NetBIOS) uses ports 137 through 139.
File Transfer Protocol (FTP) uses ports 20 and 21.
Hypertext Transfer Protocol (HTTP) uses port 80 and HTTP Secure (HTTPS) uses port 443.
You can connect to remote systems with Secure Shell (SSH) using port 22, and Remote Desktop Protocol (RDP) using port 3389.
You might like to check out the Firewall Rules and Security+ blog too.
