EIGRP stores routing-related information in three tables, each one dedicated to the organization and storage of network data. These tables are as follows:
• Neighbor table— Neighbor relationships are tracked in this table and are the basis for all of the EIGRP routing update and convergence activities.
• Routing table— Contains least-cost routes that DUAL calculated for all known destinations. EIGRP tracks up to six routes to each destination.
• Topology table— Stores all information needed to calculate a set of distances and vectors to all known and reachable destinations. This information includes the following:
- Bandwidth— The bandwidth of the slowest interface in the path to a destination.
- Total delay— The sum total of delay expected in that route.
- Reliability— The path reliability identical to the IGRP Reliability metric.
- MTU— The size of the smallest MTU supported by the router interfaces in the path. EIGRP notifies all routers in advance of the MTU on each path to a given destination.
- Reported distance— The distance reported by an adjacent neighbor to a specific destination. This metric does not include the distance between this router and the adjacent neighbor.
- Feasible distance— The lowest calculated metric to each destination.
- Route source— The identification number of the router that originally advertised that route. This field is only populated for routes learned from outside the EIGRP network.
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