ccna 200 301 official cert guide book buy

ccna 200 301 official cert guide book buy.The SPF algorithm looks for all possible routes or paths from the local router to each subnet. When a redundant path exists between the local router and some remote subnet, the SPF algorithm has to choose a better route based on the end-to-end routing metric, as shown previously in Figure 17-3.When OSPFv3 adds a route to the IPv6 routing table, the metric for that route is the second number in the routing parentheses. (The first number in the parentheses is the administrative distance (AD); IPv6 routing protocols use the same default AD value as IPv4.)17.2 Basics 367 For example, look first at two routes with a metric of 65 that R1 discovered from subnet 2001:DB8:l:23::/64, as shown in Figure 17-7. For the route through R2, R1 adds its S0/0/0 overhead 64 to R2's G0/0 overhead 1, for a total of overhead 650 R1 figures that the metric through R3 is also 65o through the default setting of maximum path 4,R1 puts both routes into the routing table. (One route uses R2 for the next hop and one uses R3.)Figure 17-7 Example of a Route from R1 to 2001:DB8:1:23::/64, Two Routes of the Same Metric 17-13 shows these two routes for subnet 2001:DB8:l:23::/64, as shown in the output of the showipv6routeospf command on router R1. Normally, routes that have learned OSPF list the next-hop link-local address. To see which route goes through R2, and which goes through R3, examine the output interface and compare it to Figure 17-7.Example 17-13 OSPFv3 Routes on R1Rl# show ipv6 route ospf ! Legend omitted for brevity0 2001:DB8:l:4::/64 [110/1]via GigabitEthernetO/1, directly connected 0 2001:DB8:l:23::/64 [110/dew]via FE80::FF:FE00:3, Serial0/0/lvia FE80::FF:FE00:2, Serial0/0/0