Before diving into the mechanics and processes of various routing protocols it is important to grasp what is exchanged when a neighbour relationship is formed. It’s easy to think that when a neighbour relationship is formed the routers just exchange the contents of the IP routing table (RIB) or even just the contents of the IGP specific table (such as the EIGRP topology table)…both assumptions would be incorrect. We’ll use EIGRP as the IGP in this example.
When the neighbour relationship is formed a flurry of updates packets are exchanged between the neighbours. These updates contain *only* the routes from the EIGRP topology table. Assuming no redistribution has been configured these routes will only be routes seeded into EIGRP with the network command.