capitulo 2 ccna 1

capitulo 2 ccna 1.Figure 10-9 Automatic SummaryLet us follow the steps in Fig.R3 uses the EIGRPauto-summary router subcommand to enable automatic summarization.R3 advertises a route for the entire Class A network 10.0.0.0, rather than separately for each subnet within network 10.0.0.0R2 learns a route in network 10.0.0.0: a route to 10.0.0.0/8 (representing the entire network 10.0.0.0), with R3 as the next-hop router.Example 10-16 shows the output of the show ip route command on R2, confirming the effect of the auto-summary setting on R3.8.3 Exam Prep 221 Example 10-16 R2 has a route for the entire network at network 10.0.0.0R2# show ip route elgrp ! lines omitted for brevityD 10.0.0.0/8 [90/2297856] via 172.16.3.3, 00:12:59, Serial0/0/0Note that auto-summarization itself does not cause any problems. In the design shown in Figure 10-9, and in the command output of Example 10-16, there is no problem.R2 can forward packets to all subnets of network 10.0.0.0, using that summarized route shown in the shaded section to send those packets to R3 at the next hop.Discontiguous There are classful networksAutomatic summarization does not cause any problems as long as the network being summarized is contiguous and not discontiguous. Residents of the United States understand the concept of discontinuity based on the common term "contiguous48 (the contiguous 48, referring to the 48 states of the United States excluding Alaska and Hawaii)". For example, to drive from the contiguous48 to Alaska, you must drive through another country. (Canada, geographically separated), so Alaska is not contiguous with the 48 states. In other words, it is not contiguous.