200-301 syllabus

200-301 syllabus.Depending on the design of the network, the failure of a single component can mean an operational outage that affects at least some users. Network engineers refer to these components as "single points of failure" when a failure causes that part of the network to shut down. For example, in Figure 6-1, the LAN has some redundant devices, but the WAN does not. If most traffic flows between these two sites, then there are many single points of failure, as shown in the figure.Figure 6-1 R1 and WAN Links as Single Points of Failure Several components are marked as single points of failure in this diagram. If any of the marked parts of the network fail, then packets cannot flow from the left network to the right. Typically, to improve availability, a network engineer first examines the design ideas to find the single point of failure. Then, choose where to add it from, so that one (or more) single point of failure has a redundancy option, which in turn enhances availability. Typically, the engineer will: . Add redundant devices and links... Implement any required features that utilize the redundant devices or redundant links. For example, for all of the single points of failure in Figure 6-1, the largest cost would be for the WAN link given the ongoing monthly expenses. However, statistically speaking, the WAN link is the component that is most likely to fail. Therefore, a reasonable escalation for the network in Figure 6-1 would beDo I already know this? Answer to the subtest.1.2 Foundation Components 129(1) d (2) c (3) a (4) c (5) b (6) c Add a WAN link and, if possible, even have the link connect to another router in the right-hand network, as shown in Figure 6-2.Figure 6-2 Higher availability, but R1 is still a single point of failureIn practice many corporate networks are designed according to Figure 6-2, with one router per remote network, two WAN links back to the primary site, and redundant routers at the primary site (right in the figure). The design scenario in Figure 6-2 has fewer single points of failure compared to Figure 6-1. Of the remaining single points of failure, one risk remains, but it is a calculated risk. For many operational outages, a router reload solves the problem and the outage is short. However, the risk still exists that when the switch or router hardware fails completely, getting a new replacement unit to the site takes time to get the site working properly again.The next step in improving remote site availability for businesses that can accept greater expense is to avoid router and switch failures that can lead to catastrophic consequences. Adding a router to the network on the left side of Figure 6-2 would resolve all of the single points of failure previously marked. Figure 6-3 gives a design scenario using a second router that is connected to a different LAN switch so that SW1 is no longer a single point of failure.VLAN 10 subnet 10.1.1.0/24Figure 6-3 Resolving all single points of failure in a network design