200 301 ccna cbt nuggets

200 301 ccna cbt nuggets.The concept of overhead from a particular switch to the root switch is easily understood. With the help of a network diagram of the root switch, the STP overhead for each port of the switch is listed, as well as the overhead of the non-root switch. The actual switches are not network diagrams; they use a different process, but network diagrams can help understand the concept.Figure 1-7 is just such a diagram, containing three switches as in the previous few diagrams. SW1 has been chosen as the root in the diagram, which considers overhead from the perspective of SW3.Figure 1-7 How to calculate the STP overhead from SW3 to the root (SW1)1.2 Basics 15SW3 sends the frame to the root switch with two optional physical paths:a direct path on the left and an indirect path through SW2 on the right. If the frame flows through a particular path, then the sum of the overhead of all switch ports through which the frame passes is the final overhead (this calculation ignores the incoming port). The comparison reveals that the overhead of a frame from SW3's port G0/1 through the direct path is 5, while the total overhead of the other path is 8. Thus SW3 uses its port G0/1 as the root port because it sends the frame to the root switch, which is the path with the best overhead.The switch comes to the same conclusion, but it uses a different handler. They add the STP overhead of their own local interface to the root overhead listed in each HelloBPDU received. the STP port overhead is an integer value assigned to each interface,VLAN, and is intended to provide an objective metric that allows the STP to choose which interface to add to the STP topology based on this value. The switch also looks at the HelloBPDUs received from each neighboring switch to see which neighboring switch claims to be the root overhead.Figure 1-8 shows the switch using the same topology diagram and STP overhead as Figure 1-7. showing an example of calculating the best root overhead and the subsequent selection of the root port. the STP calculation for SW3 calculates the overhead of going through each of the two possible paths to the root by adding the announcement overhead listed in the Hello message to the interface overhead listed in the diagram.Let's focus on the process first. The root switch sends a Hello message with a listed root overhead of 0. meaning that the root reaches itself with an overhead of 0.SW3 on the left side of the diagram has received the overhead (0) from the Hello message sent by SW1, plus the interface overhead (5) of the interface that received the Hello message.SW3 calculates that the overhead from this port (G0/1) to reach the root switch is 5.SW2, located on the right side of the figure, has been informed that the best overhead to reach the root is 4. Therefore, when SW2 forwards the Hello message to SW3, SW2 lists the root overhead as 4. SW3's STP port overhead at port G0/2 is 4, so SW3 determines that the total overhead to reach the root from G0/2 is 8.