CCNA Cram Notes & Cheatsheets

Checkout the cram notes below:

Download and post your reviews. The full version will have several sample questions with answers and explanations. You may download it here (password protected, and you need to buy the full version):

Software Defined Networking (SDN) – An Intro

Software Defined Networking (SDN) has been gaining momentum over the past few years. Important features of SDN include:

  • Separation of data and control plane,
  • a well defined vendor-neutral interface between the data and control plane (e.g. OpenFlow), and
  • a logically centralized control plane that provides a network view for the control and management applications. One important reason that industry is inclined towards SDN because it enables graceful scaling of network infrastructure and minimize obsolescence.¬† Basic differences between SDN and legacy network is shown in the diagram below:

As shown in the figure above, the user will see standardized hardware which is controlled by proprietary software (Controller), which in turn is accessed by Open APIs such as REST and HTTP. The advantage is that the network admin need not know the specific hardware command syntax and only need to know the overall design and Openflow.

We can imagine the entire SDN as having an SDN controller with North-bound and South-bound interfaces as shown in the diagram below:

As can be seen in the diagram, the SDN controller is usually proprietary to the vendor. The SDN application is a standardized application  that talks to the SDN controller, which in turn talks to the networking hardware.

The advantages of SDN include the following:

  1. Centralized network provisioning. Because it separates conceptually, the control and data planes, SDN can be used as a firewall and load-balancing traffic between networking nodes.
  2. Comprehensive infrastructure management. It is possible to provision the infrastructure such as servers, networking elements, etc. for more efficient and scalable operation.
  3. Vendor Neutrality: Enables use of old and new equipment with low obsolescence because the data plane is separated from the control pane.
  4. Enhanced security. By separating data plane from control pane, it is possible to enhance the overall security of the network. Further, SDN controller, being the brain of the Software Defined Networking, can be programmed to introduce additional layers of obscurity.
  5. Cloud infrastructure – By using SDN, the infrastructure can easily be migrated to cloud platform.

The SDN course is offered at several leading universities in USA, and typical course ware is given below:

  • API between Control Plane and Data Plane:OpenFlow
  • Controller Design:ONIX, POX and Floodlight
  • SDN Abstraction
    • Protocol Independent Forwarding
    • Composition and Trace Tree
    • Verification
    • Network Update
  • SDN Application
    • Traffic Engineering: Google B4, Microsoft SWAN, SDX
    • Wireless Networks: SoftCell, SoftRAN, OpenRadio, OpenRF
  • SDN Virtualization
    • FlowVisor
    • Open vSwitch
    • NFV
  • SDN Endhosts, Middleboxes, Debugging, fault tolerance and Security
    • SDN Control of Endhosts and Middleboxes
    • SDN Debugging, fault tolerance and Security


SimulationExams Releases Comptia A+ Practice Tests with Labsim

A+ Practice Tests with released practice tests with lab exercises for Comptia A+ certification exams preparation. This is a combined product that offers both the practice exams as well as the labs for hands-on practice. The software is useful for practicing A+ exams along with simultaneous labs preparation. The practice tests features are given below:

  • 300+¬† exam-like questions
  • Custom exam settings
  • Detailed explanations and online feedback
  • Learn mode and exam mode to suit your requirement
  • Identify weak areas
  • Key concepts flashcards for each question
  • Check for updates online
  • Online feedback (from within the exam) and support site
  • Licenses never expire

The Labsim provides several labs for hands-on experience. Practice safely without having the fear that the system might crash due to wrong settings! Since the labsim is a virtual networking environment, you can safely practice settings such as changing the control pane/networking/user controls without crashing the system or the Wifi router. A few screenshots of the labsim is given below:

a) Labsim Intro Form: Given below is an introductory text about the labsim

a+ labsim main window Currently about 75 labs are available with free demo version and detailed lab manual. Download the free version and install: A+ practice tests with labsim


The main window of the labsim is shown below:

The left pane shows the available labs. You can expand the labs in any given topic by clicking on the + sign. The right pane shows the selected lab. In this specific instance of lab, you are required to drag and drop relevant text to corresponding graphic element in the diagram. The topics covered in the labsim are given below:

  • PC Hardware
  • Networking
  • Laptops and mobiles
  • Operating systems
  • Printers and Scanners
  • Security
  • Troubleshooting

Each of the above topics contain several labs for practice. It may be noted that chapter-end questions are provided in the Essentials manual.

Checkout complete details about the labs by going to the product URL: Comptia A+ Practice Tests with Labsim