Common process found in routing protocols

Reception of routing information from neighbours: / exchange routing updates and form neighbours

Though the use of routing updates, each routing protocol learns path to other subnets which are not directly connected.

Updates are exchanged with layer 2 adjacent devices called neighbours, some IGP protocols such as EIFRP, OSPF, IS-IS protocol form a neighbour relationship before exchanging routing updates, where as other routing protocols such as RIV2 exchange routing information without forming neighbours with adjacent devices.

Routing protocol data structures:  / store routing updates in there data structure

All modern routing protocols have data structures where they store information received from there neighbours in the form of routing updates including the directly connected or static routes as well as external routes which are redistributed.  Some older routing protocols such as RIV does not have data structures and thus installs and stores route directly into the routing table.

Route injection or redistribution :

All IGPS inject routes into their data structures,  injected routes are those which are either directly connected or static routes, by directly connected I am referring to interfaces where the routing protocol has been enabled.

External routes which are learned from other sources can also be redistributed into data structures and then advertised to neighbours.

Route selection and installation:

Each routing protocol will select a best path for a prefix from its data structure,  different routing protocols use different algorithm to select its best path, best path selection is based on routing protocol metrics.

Each routing protocol offers its best path for a prefix to the ip routing table, if multiple  routing protocols offer best path for the same prefix, path with the least administrative distance will get installed in the routing table.

Transmission of routing information to neighbours:

Routing information which is stores in data structures , injected or static routes as well as external routes which are redistributed in data structures is then advertised to neighbours, as mentioned in the reception of routing information from neighbours, IGP's require a neighbour relationship before they start exchanging routing information, where as other routing protocols such as RIPv2 does not require neighbour relationship for exchanging routing updates.