best 200-301 ccna book

best 200-301 ccna book.Step 1 Neighbor Discovery: The EIGRP router discovers potential neighboring EIGRP routers by sending Hell. messages, and performs basic parameter checks on them to determine whether they become neighbors. The neighbor is added to the EIGRP neighbor table after passing all the parameter checks. Step 2 Topology Exchange: When the neighbor relationship is established complete topology updates are exchanged between neighbors, after which only local updates are exchanged depending on network topology changes. The data obtained in these updates is added to the EIGRP topology table. Step 3 Routing: Each router analyzes the respective EIGRP topology table and selects the route with the minimum metric value to reach each subnet. EIGRP places the route with the best metric to each destination into the IPv4 routing table. The second major section of this chapter discusses how EIGRP uses these three steps to build its own routing table. Although the process of these three steps looks a lot like OSPF, the details of their content are very different, especially since OSPF has to use LS logic to process topology data while EIGRP does not process it at all. In addition to these three steps, this subsection describes some of the special logic that EIGRP uses to converge and react to changes in the interconnected network - logical approaches that are not seen in other types of routing protocols.1. EIGRP's NeighborsAn EIGRP neighbor is another EIGRP-speaking router connected to a common subnet with which it is willing to exchange EIGRP topology information.EIGRP dynamically discovers potential neighboring routers by sending an EIGRP Hello message to the multicast IP address 224.0.0.10. Routers are informed of potential neighbors by receiving Hello messages.Before deciding to become an EIGRP neighbor with a router, the router performs some basic checks on each potential neighbor. A potential neighbor is a router that has received an EIGRP Hello from that router. The router then decides whether to allow a neighbor with that router by verifying the following settings. ,. --.... Must pass authentication.f |g. the same AS number settings must be used.. The source IP address used for the Hello sent by the neighbor must be on the same subnet.Tip: The router's EIGRP K values should also match. but the issue is beyond the scope of this book.EIGRP authentication verification of neighbors is relatively straightforward. If authentication has been configured. both routers must use the same authentication type and key. the EIGRP configuration contains an Autonomous System Number (ASN) parameter that must be the same in both neighboring routers. Finally, the IP addresses used to send EIGRP Hello messages, that is, the IP addresses of the respective interfaces of the two routers, must each be within the IP address range of the subnet to which the other router is connected.EIGRP neighbor relationships are much simpler than OSPF's. EIGRP has no additional concept of full adjacency similar to OSPF, nor does it have a neighbor state similar to OSPF. Once an EIGRP neighbor is discovered and passes basic authentication verification, that router becomes a neighbor. From this point on, these two routers can start exchanging topology information.2. EIGRP Topology Information Exchange