feat(vpc): start new routing concepts

Author: RoRoJ

pages/vpc/concepts.mdx

@@ -9,7 +9,7 @@ tags: network vpc virtual-private-cloud regional private network routing
 categories:
   - network
 dates:
-  validation: 2024-12-03
+  validation: 2025-05-01
   posted: 2023-02-06
 ---
 
@@ -105,11 +105,19 @@ Routes can be of the following types:
 
 When deciding which route to apply, the route table reads the routes from most specific to least specific, in terms of destination IP range. The first matching route encountered is the one that determines the path for the traffic. Therefore, a route to destination `172.16.8.0/22` is applied before a default route to `0.0.0.0/0`.
 
+Each route in a route table has a **scope**: it may be advertised across the entire VPC, or on certain Private Networks only.
+
 ## Routing
 
-Routing allows Private Networks in the same VPC to communicate with each other, via managed and custom routes. Routing is activated by default whenever you create a new VPC, and can be activated on pre-existing VPCs by [following these steps](/vpc/how-to/manage-routing/#how-to-activate-routing).
+Routing allows resources on Private Networks witin the same VPC to communicate with each other, via managed and custom routes. Routing is activated by default whenever you create a new VPC, and can be activated on pre-existing VPCs by [following these steps](/vpc/how-to/manage-routing/#how-to-activate-routing).
+
+Each routed VPC has a [route table](#route-table) which is automatically populated with routes to each of its Private Networks. When you attach a Public Gateway to a Private Network, and tell it to advertise a default route to the internet, such routes are also added to the VPC's route table. You can also create your own [custom routes](/vpc/how-to/manage-routing/#how-to-create-a-custom-route), to route traffic towards defined destination IP ranges towards specific "next hop" resources.
 
-Each routed VPC has a [route table](#route-table) which is automatically populated with routes to each Private Network in the VPC, as well as to any attached Public Gateways. These routes allow the VPC to automatically route packets between its Private Networks, or from a given Private Network to its attached Public Gateway when the destination is outside the VPC. You can also create your own [custom routes](/vpc/how-to/manage-routing/#how-to-create-a-custom-route).
+<Message type="note">
+If you have [updated](TODO) routing behavior on your VPC, or created a VPC since TODODATE, routing takes on the following characteristics:
+- Custom routes are advertised across the entire VPC, instead of only on the Private Network of the resource designated as next hop.
+- You can optionally [enable each Private Network in the VPC to receive default route advertisements](TODO) not only from their locally attached Public Gateways, but from other Public Gateways (or default custom routes) attached to different Private Networks throughout the whole VPC. 
+</Message>
 
 Read more about how routing works in [our detailed guide](/vpc/reference-content/understanding-routing/).