ccna guide book pdf

ccna guide book pdf.by.16.1.5 EIGRP's SIA and the Qualification of the Lookup RangeAs an advanced distance vector protocol, EIGRP relies on its neighbors to provide routing information, and when a route is lost, the EIGRP router will look for a feasible successor in the topology table, and if found, instead of switching the original route to the active state, it will promote the feasible successor to a successor . and put the route into the routing table without recalculating the route using the DUAL algorithm. If there is no feasible successor in the topology table, the route is placed in the active state and the EIGRP router sends a query to all neighboring routers (except the one that reaches the successor. horizontal split restriction) in order to find a route that can be replaced. If the queried router knows of an alternative route, it puts this alternative route into an answer packet and sends it to the source router that sent the query. If the router receiving the query does not have information about an alternative route, it continues to send it to its other neighbors until it finds a route that can be substituted. Because EIGRP uses reliable multicast to find alternative routes, the router must receive answer packets from all routers queried before it can recalculate the route. If there is a router whose answer packet has not been received, the source router that sent the queryChapter 16 EIGRP .275 .It must wait. by default. if some router does not respond to the query within 3 minutes. this route enters the SIA (Stuck inActive) state. the router then resets its neighbor relationship with this router that did not respond. To avoid the SIA scenario or to reduce the frequency of S1A, the range of queries must be limited, usually in two ways, either by configuring route summarization on the outgoing interface of the router, or by configuring the remote router as an EIGRP Stub router, the contents of which are beyond the scope of this book.16.1.6 Introduction to IPv6 EIGRPIPv6 EIGRP is similar to IPv4 EIGRP in that it populates the IPv6 routing table by exchanging routing information. IPv6 EIGRP also uses DUAL as the computation engine to ensure that loop-free paths and loop-free alternate paths are properly used throughout the routing domain. IPv6's E1GRP has different processes than IPv4, and the processes and operations are essentially the same as those of the IPv4 routing protocol, but they operate independently. A comparison of the main functions of EIGRP for IPv4 and EIGRP for IPv6 is shown in Table 16-1.Table 16-1 Comparison of the Main Functions of EIGRP for IPv4 and EIGRP for IPv6EIGRP for IPv4 EIGRP for IPv6Notification Routing IPv4 Network IPv6 Prefix