Introducing EIGRP DUAL参考.pptVIP

Configuring EIGRP Introducing EIGRP DUAL Outline Overview Selecting a Successor by DUAL Selecting a Feasible Successor by DUAL Performing Route Selection When No Feasible Successor Is Available What is the EIGRP Query Process? Lesson Summary EIGRP DUAL The DUAL finite state machine decision process is as follows: Tracks all routes advertised by neighbors跟踪所有邻居路由器的路由通告 Selects loop-free path using a successor and remembers any feasible successors选择无环路由,并将下一跳作为后继者,同时记录其它的可行后继者 If the successor is lost, uses a feasible successor如果后继者丢失,那么则使用可行后继者的路由 If there is no feasible successor, queries neighbors and recomputes a new successor如果这里没有可行后继者,那么则查询邻居路由器并且重新计算新的后继者 EIGRP Successor EIGRP Feasible Successor Feasible Successor Route No EIGRP Feasible Successor DUAL Example: Start DUAL Example: Link Goes Down DUAL Example: D Sends Queries DUAL Example: E Sends Queries DUAL Example: C Replies DUAL Example: E Replies DUAL Example: Convergence Summary The best route (successor) is selected from the lowest-metric (advertised distance) loop-free path with up to four successors added to the routing table. The backup route (feasible successors) is the lowest AD metric from the next-hop routers provided its AD value is less than the FD value of the current router. If there is no feasible successor for a given network and the pathway through the successor becomes unavailable, a query-and-reply process is automatically executed to find a loop-free pathway to the lost network. When a feasible successor cannot be found in the topology table, the router sends queries to neighboring routers looking for a new successor. Configuring EIGRP Using EIGRP in an Enterprise Network Factors That Influence EIGRP Scalability Quantity of routing information exchanged between peers; without proper route summarization, this can be excessive. Number of routers that must be involved when a topology change occurs. Depth of topology: the number of hops that information must travel to reach all route