200-301 passed

200-301 passed.5.1 "Do I Know This Already?" Mini-TestThe chapters on troubleshooting in this book cover concepts from many other chapters and even include some chapters from the CCENT/CCNAICND1 (100-101) Certification Exam Guide, along with answers to some of the more difficult questions on the CCNA exam, so readers should read these relevant chapters first, regardless of their current level of knowledge. Because of this, none of the troubleshooting chapters have a "Do I Know This Already?" quizzes. Of course, if you have a complete grasp of the IP routing troubleshooting content in this book and the CCENT/CCNAICND1 (100-101) Certification Exam Guide, you can skip most of this chapter and read the "Exam Prep" content directly.5.2 Fundamentals5.2.1 Problems Between the Host and Default RouterSuppose you are a customer support representative (CSR) handling calls from users with various problems. A user leaves a message saying that he cannot connect to the server. You call and cannot reach him, so you perform a series of pings from the host's default router, using the strategy for isolating the problem described in Chapter 4.After the pings, you believe that the problem exists between the user's device and the default router-for example, between router R1 and host A, as shown in Figure 5-1 shows.106 Chapter 4, Part 1 Troubleshooting IPv4 RoutingDefault Router DNS Server Figure 5-1 Focus of Discussion in this Chapter Section The first section of this chapter focuses on issues that occur at the host, the default router, and in between. First, this section looks at the host itself and its four IPv4 settings, as shown in Figure 5-1. After that, the discussion continues around the LAN interface to the default router, and several settings that are critical to being the host's default router.Problems Caused by Host IPv4 Settings ItemsA typical IPv4 host can obtain its four critical IPv4 settings by either of two methods: static configuration or by using DHCP. in fact, in both cases, the settings can also be incorrect. Frankly, because of human error in entering values, any static setting item can be set to the wrong number. More surprisingly, DHCP can also be set to the wrong value: the DHCP process works fine, but uses a value misconfigured on the DHCP server, so it is actually possible for the host to get some incorrect IPv4 settings.This section will first examine the settings on the host and what they should match, followed by a discussion of typical problems. Ensuring IPv4 Settings Match CorrectlyOnce the engineer determines that the problem is between the host and its default router, he or she checks the host IPv4 settings against the other settings that should be in place. To start this process, either use the host OS's GUI to guide the user, or use the host OS's native command line commands, such as ipconfig and ifconfig. This process will reveal some obvious problems (such as parameters missing altogether) or, if DHCP is used, a complete failure of DHCP, and thus the inability to obtain any IPv4 settings.