200-301 braindumps pdf

200-301 braindumps pdf.Troubleshooting the data platform should be careful to observe the two-way flow of data between the two devices. One device sends data, and the receiving device usually sends some sort of duplicate message. A problem like "I can't talk to Serverl" can be caused by packets being sent from the user to Serverl. But such a problem can also be generated during the corresponding flow of packets from Serverl to the user. So, to thoroughly understand how useful communication occurs, you also have to reverse the analysis.Unless you can associate a specific root cause of failure for this problem from a specific surface phenomenon of failure, troubleshooting the data platform should begin with analysis of the Layer 3 data platform. If you start the analysis at Layer 3, you can learn the main processes of sending and receiving data between the two hosts. Thus, it is possible to more clearly examine each step of the Layer 3 step-by-step forwarding, and thus observe the more basic Layer 1 and Layer 2 details. For example, Figure 3-1 shows the six major steps of IP forwarding (data platform) in a small network.Figure 3-1 Key Steps in the IP Forwarding Example If you want to understand the expected operation of Layer 3 in this example, you need to consider how packets flow from left to right and how answer messages flow from right to left. The specific analysis of the 6 steps in the figure is described below. Step 1 Considering the IP addresses and masks of PC1 and PC2 and the logical relationship of PC1, it can be determined that PC2 is in another subnet. This will then make PC1 choose to send the packet through its default gateway (R1). Step 2 considers R1's forwarding logic by matching the packet destination IP address to R1's routing table, and can anticipate R1's next choice to send the packet to R2. Step 3 considers the same logical relationship of routing table matches on R2 as in the previous step of the R1 analysis, but this time using R2's routing table. The matching table entry should be a directly connected route on R2. Step 4 This step of the analysis is related to PC2's reply packet and applies the same basic logic as Step 1. By comparing the IP address/mask of PC2 with the IP address of PC1, it can be determined that the two are on different subnets. Therefore, PC2 will send the packet to its default gateway, R2. step 5 Think about the packet forwarding logic of R2, whose destination address is the IP address of PC1, and thus by matching the route you can anticipate R2 sending the packet to R1 next. step 6 The final step of routing occurs on R1, and since the destination address of the packet is the IP address of PC1, matching this IP address to a A direct route is matched, causing R1 to send the packet directly to PC1's MAC address.Having fully appreciated how each step of Layer 3 is expected to work, it is time to examine Layer 2 more closely. Following the same order of analysis as before, look even further at step 1 of Layer 3 routing (PC1 sends a packet to R1) and examine the workings of Layer 1 and Layer 2 as the frame sent by PC1 is delivered to R1, as shown in Figure 3-2.52 Chapter 3 Troubleshooting LAN SwitchingSTP blockingFigure 3.2 Main steps of the LAN switch forwarding exampleThis analysis process also starts with PC1, this time considering the Ethernet headers and tails, in particular the source MAC address and the destination MAC address. Then, think about the forwarding logic relationship of SW1 in step 2. By comparing the destination MAC address of the frame with the MAC address table of SW1, it is clear that the forwarding logic is that SW1 forwards the frame to SW2. step 3 and step 4 then repeat the application of the logic approach of step 2 for SW2 and SW3 respectively.(2 ) Control Platform AnalysisMany control platform processes directly affect the data platform processes. For example, IP routing cannot work without a suitable IP path, so routers generally use a dynamic routing protocol (i.e., a control-platform protocol) to learn routes. Routing protocols are considered control-platform protocols in part because the application of routing protocols eliminates the need for repeated processing of each frame or packet.