CCNA Layer by Layer

Hello CCNA Candidates!

My goal is to break down each Topic of the CCNA by TCP/IP layers in order to fully explain everything listed by Cisco in their official exam topics. If you want a structured and logical aproach to understanding the theory and concepts in the CCNA, you're in the right place. I recommend starting with this and then moving on to another resource for practical knowledge, using labs with packet tracer for example. For anyone who is just beginning in networking, the following shows the OSI & TCP/IP models which are absolutely necessary to understand!

              OSI Model:                                    TCP/IP Model:
	   Layers		     PDUs               Layers		     PDUs
  	------------------------------------         ------------------------------------
	1) Physical: 		 Bit               1) Physical: 	 	 Bit
	2) Data Link: 		 Frame         2) Data Link: 		 Frame
	3) Network: 		 Packet	    3) Network: 		 Packet
	4) Transport: 		 Segment     4) Transport: 		 Segment
	5) Session: 		 Data	    5) Application: 	         Data
	6) Presentation:	 Data
	7) Application: 	 Data
	* PDU (Protocol Data Unit)