Something I very recently learned is that routing protocols are learned on Control Planes.
Also, welcome to possibly the last post of 2019. I need a break too!
There's plenty more coming in 2020. Meanwhile, visit and follow the new LinkedIn Company Page, if you please.
Many of these protocols will have very similar commands - network [network] wildcard [wildcard] - and OSPF has areas.
An area limits the scope of route information distribution. - mainly, less routes to propagate by summarizaton.
Look back at the image; The middle router, 4(2), is what we call a backbone area, that has interfaces in both area 1 (Router 4(1)) and area 2 (Router4).
Area 3 up there is a non-entity.
Here are the outputs for show ip ospf for each router: Backbone;
All three areas are acknowledged, even our interfaceless area 3 up there.
Area 1 (left):
Area 2 (right):
You may have noticed "Routing Process "ospf 1" and have been confused - processes and areas aren't the same thing. Processes are more for us to know what group of routers we may be working with.