200-301 quiz

200-301 quiz.Figure 5-13 Using the same subnet in two different places based on the subnet ID calculated in Figure 5-12 (as is also the case in Figure 5-13) violates IPv4 addressing rules because it confuses the router as to where to send the packets. In this example, for packets to be sent to subnet 10.L1.128/25, some routers will send them to R3, while others will assume that the best route is to R4. Assuming that all routers use the same routing protocol (such as OSPF), then both R3 and R4 will broadcast a route to 10.1.1.128/25. In this example, R1 and R2 might send packets to two different instances of subnet 10.1.1.128/25. With these routes, the host near R1 is able to communicate with the host 10.1128/25 on the LAN outside R4, but not outside R3LAN, and vice versa. Finally, although the symptoms indicate some sort of routing problem, the cause is an invalid IP addressing plan. the IP addressing plan should not use the same subnet on different LANs, as in this use case. The solution is to change R3 or R4 so that it uses different subnets on the LAN interfaces.5.2 Basics 119and non-overlapping subnets.Overlap when using VLSM When using VLSM, the same type of addressing errors can result in overlapping subnets; this can be more difficult to detect. First, overlap between subnets that have different masks can only result in partial overlap. That is, the two overlapping subnets have different sizes andThere may also be different subnet IDs. overlap occurs for all addresses in the smaller subnet, but this is only a portion of the larger subnet. Second, the inter-host problem appears only at certain addresses (especially the subnet addresses within the overlap), making it more difficult to detect the problem. For example, Figure 5-14 shows an example of a VLSM overlap. The figure shows only the IP address/mask pairs for the router and host interfaces. First, take a closer look at the example and try to find the overlap by IP address.Figure 5-14 VLSMIP Addressing Plan in Network 172.16.0.0 To find the overlap, the person responsible for troubleshooting needs to analyze the individual subnets to find not only the subnet IDs, but also the subnet broadcast addresses and address ranges within the subnets. If the analysis is limited to looking at the subnet IDs, then the overlap may not be noticed (as in this example).Figure 5-15 shows the very first analysis of each subnet, listing only the subnet IDs. note that the two overlapping subnets have different subnet IDs, but the lower right subnet (172.16.5.0/24) and part of the upper right subnet (172.16.4.0/23) overlap completely. (Subnet 172.16.4.0/23 has a subnet broadcast address of 172.16.5.255, and subnet 172.16.5.0/24 also has a subnet broadcast address of 172.16.5.255)Clearly, the actual subnets have overlapping address ranges, which is incorrectly designed and should be corrected. However, once implemented, the symptoms appear similar to routing issues, such as similar use cases that do not use VLSM. For some hosts only (but not all), the ping command fails, but the traceroute command is able to complete.Figure 5-15 Example of VLSM Overlap but with Different Subnet IDs Configuring Overlap VLSM Subnet IP Subnetting requires that the address ranges of subnets in an interconnected network not overlap. When the new ip address command creates an overlapping120 Chapter 5, Part 2 Troubleshooting IPv4 Routing