Q:

Communication between networks without routing - is it possible?

Could someone please tell me if my understanding is correct?
I created 2 simple networks in Packet Tracer and "wired" them together with router. I have not set up any routing (neither static nor dynamic) for the router. And yet both of my networks can communicate with each other.
Is this proper behaviour ?
The only thing I can think of is that router knows all networks that are connected to it so within it there is no need for setting up routing protocols.
But still, I remember when I was told that for two networks to communicate there is need of a router (and implicitly I assumed routing protocols are required).

A:

Routing protocols are used by routers to communicate their routes with each other.  
If you only have one router, there is no one for that router to talk to, and therefore no need for routing protocols.
Don't confuse routing - forwarding based on layer 3 information
with routing protocols -- a method for routers to communicate their reachability.

