If you’re planning on taking the Security+ exam, you should have a basic understanding of protocols used with VPNs. For example, can you answer this question?
Q. Your organization is planning to implement a VPN and wants to ensure it is secure. Which of the following protocols is the BEST choice to use with the VPN?
A. HTTP
B. SFTP
C. IPsec
D. PPTP
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.
Connecting via Remote Access
The following figure shows three examples of how users can connect to internal networks from remote locations. The first VPN client connects to the Internet using a broadband connection to an Internet Service Provider (ISP), and the second VPN client connects to the Internet using a dial-up connection to an ISP. The third client bypasses the Internet and instead uses a dial-up connection directly to the RAS server.
Connecting to a VPN server and a RAS server
The figure shows the VPN server and RAS server between two firewalls (configured as a DMZ). The firewalls provide some protection for the servers and the private network. The VPN server is reachable through a public IP address, making it accessible from any other host on the Internet and the RAS server is reachable through a phone line. Both the VPN server and RAS server use an internal RADIUS server to authenticate clients before granting them access to the internal network.
Of course, the firewall access control lists (ACLs) need to include rules allowing the traffic. The ports you open are dependent on the tunneling protocols used for the VPN.
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.
IPsec as a Protocol Used with VPNs
IPsec supports Tunnel mode, which encrypts the entire IP packets, and is the mode used with VPNs. Transport mode only encrypts the payload within the IP packets and is used within private networks.
IPsec provides security in two ways:
- Authentication. IPsec includes an Authentication Header (AH) to allow each of the hosts in the IPsec conversation to authenticate with each other before exchanging data. AH provides authentication and integrity. AH uses protocol ID number 51.
- Encryption. IPsec includes Encapsulating Security Payload (ESP) to encrypt the data and provide confidentiality. ESP includes AH so it provides authentication, integrity, and confidentiality. ESP uses protocol ID number 50.
The term protocol ID number may look like a typo, but it isn’t. AH and ESP are identified with protocol ID numbers, not port numbers. A basic packet-filtering firewall can filter packets based on IP addresses, ports, and some protocols, such as Internet Control Message Protocol (ICMP) and IPsec. Packet filters use the protocol ID numbers to identify AH and ESP traffic.
IPsec uses Internet Key Exchange (IKE) over port 500 to authenticate clients in the IPsec conversation. IKE creates security associations (SAs) for the VPN and uses these to set up a secure channel between the client and the VPN server.
Remember this
IPsec is a secure encryption protocol used with VPNs. Encapsulating Security Payload (ESP) provides confidentiality, integrity, and authentication for VPN traffic. IPsec uses Tunnel mode for VPN traffic and can be identified with protocol ID 50 for ESP. It uses IKE over port 500.
L2TP and IPsec
Cisco and Microsoft joined forces to create the Layer 2 Tunneling Protocol (L2TP). Although it is possible to use L2TP to create a tunnel between devices, L2TP doesn’t include any encryption, so it does not provide confidentiality of the data. However, you can combine IPsec with L2TP (as L2TP/IPsec) to provide security for the VPN tunnel. L2TP uses UDP port 1701.
NAT and IPsec
IPsec and Network Address Translation (NAT) are not compatible with each other. NAT manipulates the IP header of the packets when it translates the IP addresses. This change causes the receiving end of the VPN tunnel to discard the packet as invalid.
If the path to the VPN server is through a device using NAT, you need to look for alternatives. NAT Traversal (NAT-T) is one possible choice, or you could use another tunneling protocol.
Q. Your organization is planning to implement a VPN and wants to ensure it is secure. Which of the following protocols is the BEST choice to use with the VPN?
A. HTTP
B. SFTP
C. IPsec
D. PPTP
Answer is C. Internet Protocol secure (IPsec) is one of several protocols used to secure virtual private network (VPN) traffic. It is the best choice of the available answers.
Hypertext Transfer Protocol (HTTP) doesn’t provide any security.
Secure File Transfer Protocol (SFTP) secures FTP transmissions but not VPNs.
Point-to-Point Tunneling Protocol (PPTP) is an older protocol used with VPNs, but it is not as secure as IPsec.
