What is ospf routing protocol pdf

If the router does what is ospf routing protocol pdf contain a valid path to the destination, the traffic is discarded. Routers that are connected to this router indirectly, through another router are not recorded in this table as they are not considered neighbors. Topology Table: The topology table stores routes that it has learned from neighbor routing tables.

Unlike a routing table, the topology table does not store all routes, but only routes that have been determined by EIGRP. The topology table also records the metrics for each of the listed EIGRP routes, the feasible successor and the successors. Routes in the topology table are marked as “passive” or “active”. Passive indicates that EIGRP has determined the path for the specific route and has finished processing. Active indicates that EIGRP is still trying to calculate the best path for the specific route. Routes in the topology table are not usable by the router until they are inserted into the routing table. If the network changes, for example, a physical link fails or is disconnected, the path will become unavailable.

EIGRP is designed to detect these changes and will attempt to find a new path to the destination. The old path that is no longer available is removed from the routing table. EIGRP does not send its routing table periodically, but will only send routing table data when an actual change has occurred. EIGRP is mostly considered a hybrid protocol.

EIGRP is connected to another router also running EIGRP, information is exchanged between the two routers and a relationship is formed known as an adjacency. The entire routing table is exchanged between both routers at this time. After this has occurred, only differential changes are sent. EIGRP is often considered a hybrid protocol because it is also sends link state updates when link states change.

Routes are not summarized at the classful network boundary unless auto summary is enabled. The ability to use different authentication passwords at different times. Sends topology changes, rather than sending the entire routing table when a route is changed. Periodically checks if a route is available and propagates routing changes to neighboring routers if any changes have occurred. Backwards compatibility with the IGRP routing protocols. EIGRP determines the value of the path using five metrics: bandwidth, load, delay, reliability and MTU. EIGRP router updates are delivered to all neighbors completely.

Cisco Systems now classifies EIGRP as a distance vector routing protocol, but it is normally said to be a hybrid routing protocol. IP-EIGRP topology entry for 10. Number of routers a packet passes through when routing to a remote network, used to limit the EIGRP AS. EIGRP maintains a hop count for every route, however, the hop count is not used in metric calculation. Routes having a hop count higher than the maximum will be advertised as unreachable by an EIGRP router. The composite routing metric calculation uses five parameters, so-called K values, K1 through K5. These act as multipliers or modifiers in the composite metric calculation.

K1 is not equal to Bandwidth, etc. By default, only total delay and minimum bandwidth are considered when EIGRP is started on a router, but an administrator can enable or disable all the K values as needed to consider the other Vector metrics. Cisco routers running EIGRP will not form an EIGRP adjacency and will complain about K-values mismatch until these values are identical on these routers. The interface delay is a configurable static parameter expressed in tens of microseconds. EIGRP takes this value directly without scaling into the weighted formula. Therefore, if given a delay value in microseconds, it must first be divided by 10 before using it in the weighted formula. IGRP, the formula does not contain the scaling factor of 256.