Server Ports Versus Client Ports

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Ports are logical numbers used by TCP/IP to identify what service or application should handle data received by a system. Do you know the differences between server ports and client ports? You should if you plan to take the Security+ exam. This post should help.

Here’s a sample Security+ practice test question:

Q. You recently learned that a network router has TCP ports 22 and 80 open, but the organization’s security policy mandates that these should not be accessible. What should you do?

A. Disable the FTP and HTTP services on the router.

B. Disable the DNS and HTTPS services on the router.

C. Disable the SSH and HTTP services on the router.

D. Disable the Telnet and Kerberos services on the router.

Can you answer the question? 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.

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INCLUDES QUESTIONS TO HELP YOU PREPARE

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Bonus - Performance Based Questions

Additional Security+ questions to help you prepare for the new performance based questions. These are included with the full bank of Security+ practice test questions and are divided into different sections. For example, you'll have access to the following links:

- Performance Based Question - Set 1

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of security to mobile devices and servers in a data center. You'll then have two questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

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- Performance Based Question - Set 5

You'll see a graphic explaining what you might be required to do on the actual exam to match protocols and ports. You'll then have seven questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 6

You'll see a list of security controls along with a graphic showing devices and locations within an organization, along with instructions on what you might be required to do on the actual exam to match the controls with the devices and locations. You'll then have four questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 7

You'll see a list of authentication methods and authentication factors along with instructions on what you might be required to do on the actual exam to match the authentication methods with the authentication factors. You'll then have six questions that test your knowledge and ability to correctly answer the questions. This set also includes a link to a graphic showing the end solution for the overall performance based question simulation.

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You'll see a graphic explaining what you might be required to do on the actual exam to match different types of attacks with the name of the attack type. You'll then have five questions that test your knowledge and ability to correctly answer the questions. This is similar to Set 2 but expands on the possibilities. The set also includes a link to a page showing the end solution for the overall performance based question simulation.

New - Performance Based Question - Set 9

New questions recently added using a different testing engine. See a demo here. This set includes drag and drop and matching questions on ports.

New - Performance Based Question - Set 10

A random set of 20 performance-based questions using drag and drop, matching, sorting, and fill in-the blank. This set includes performance-based questions on RAID.

Get the full bank of Security+ Practice Test Questions Here

Get the full bank of Security+ Practice Test Questions

Combining the IP Address and the Port

At any moment, a computer could be receiving dozens of packets. Each of these packets includes a destination IP address and a destination port. TCP/IP uses the IP address to get the packet to the computer. The computer then uses the port number to get the packet to the correct service, protocol, or application that can process it.

For example, if the packet has a destination port of 80 (the well-known port for HTTP), the system passes the packet to the process handling HTTP. It wouldn’t do much good to pass an SMTP email packet to the HTTP service or send an HTTP request packet to the SMTP service.

Server Ports

IP Address Used to Locate Hosts

Imagine that the IP address of GetCertifiedGetAhead.com is 72.52.206.134, and the address assigned to your computer from your ISP is 70.150.56.80. TCP/IP uses these IP addresses to get the packets from your computer to the web server and the web server’s answer back to your computer.

There’s a lot more that occurs under the hood with TCP/IP (such as DNS, NAT, and ARP), but the main point is that the server’s IP address is used to get the requesting packet from your computer to the server. The server gets the response packets back to your computer using your IP address (or the IP address of your NAT server).

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Online access includes all of the content from the

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  • Introduction
  • About the exam (including types of questions and strategies for performance-based questions)
  • 100 question pre-assessment exam
  • Mastering Security Basics (full content from Chapter 1 of the study guide including the exam topic review and 20 practice test questions)
  • Exploring Control Types and Methods (full content from Chapter 2 of the study guide including the exam topic review and 20 practice test questions)
  • Understanding Basic Network Security (full content from Chapter 3 of the study guide including the exam topic review and 20 practice test questions)
  • Securing Your Network (full content from Chapter 4 of the study guide including the exam topic review and 20 practice test questions)
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Test your readiness with these quality materials

Random 100-question tests

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Eight sets of performance-based questions with multiple questions in each set. These questions help you understand and prepare for performance based questions.

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Server Ports

Different protocols are enabled and running on a server. These protocols have well-known or registered port numbers, such as port 22 for SSH, 23 for Telnet, 80 for HTTP, 443 for HTTPS, and so on. When the system receives traffic with a destination of port 80, the system knows to send it to the service handling HTTP.

Any web browser knows that the well-known port for HTTP is 80. Even though you don’t see port 80 in the URL, it is implied as http://GetCertifiedGetAhead.com:80. If you omit the port number, HTTP uses the well-known port number of 80 by default.

Popular web servers on the Internet include Apache and Internet Information Services (IIS). Apache is free and runs on Unix or Linux systems. Apache can also run on other platforms, such as Microsoft systems. IIS is included in Microsoft Server products, such as Windows Server 2008 and Windows Server 2012. All of these web servers use port 80 for HTTP. When the server receives a packet with a destination port of 80, the server sends the packet to the web server application (Apache or IIS) that processes it and sends back a response.

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Client Ports

TCP/IP works with the client operating system to maintain a table of client-side ports. This table associates port numbers with different applications that are expecting return traffic. Client-side ports start at port 49,152 and increment up to 65,535. If the system uses all the ports between 49,152 and 65,535 before being rebooted, it’ll start over at 49,152.

When you use your web browser to request a page from a site, your system will record an unused client port number such as 49,152 in an internal table to handle the return traffic. When the web server returns the web page, it includes the client port as a destination port. When the client receives web page packets with a destination port of 49,152, it sends these packets to the web browser application. The browser processes the packets and displays the page.

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Q. You recently learned that a network router has TCP ports 22 and 80 open, but the organization’s security policy mandates that these should not be accessible. What should you do?

A. Disable the FTP and HTTP services on the router.

B. Disable the DNS and HTTPS services on the router.

C. Disable the SSH and HTTP services on the router.

D. Disable the Telnet and Kerberos services on the router.

Answer is C. You should disable the Secure Shell (SSH) and Hypertext Transfer Protocol (HTTP) services because they use TCP ports 22 and 80 by default.

File Transfer Protocol (FTP) uses ports 20 and 21. Domain Name System (DNS) uses port 53.

Telnet uses port 23.

Kerberos uses port 88.

See Chapter 3 of the CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide for more information on  basic network security.

You may also like this post on Security+ Ports. It includes tables matching many protocols with their well-known ports and also identifies if it is using TCP or UDP.

The Identifying Ports in Logs post combines information related to the TCP three-way handshake. It helps you understand the direction of the traffic (to or from the server) by identifying the elements (syn, syn/ack, ack) in the handshake within a log entry.

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