OSPF - what to put in one area

RouterOS Forwarding Protocols
1

I’m thinking about migrating my network from RIP to OSPF.

After reading about OSPF, I’m confused about what to put in one area: all routers in one broadcast domain, all routers in one location or something else ?
Or simply put everything in backbone and don’t care ?

2

You need areas to join certain group of routers inside an Autonomous System

Some vendors recommend to join in groups of 40-50, i have done deployment with 5-10 of router per area and it works fine.

There are to many advantages of this:
Summarize networks to send only sumarize route to backbone area
Make routing filters per area.

Backbone area or area 0 is the principal and all area need connection with it

3

For ISP networks, it’s helpful to break up the routers that are customer facing and not in the core for a few reasons.

  1. As already mentioned summarization.
  2. The SPF algorithm runs within an area so Area boundaries help to limit instability is a router starts sending bad LSAs or is flapping. This helps to protect the core.
  3. Once the number of routers is over 150 to 200, OSPF will be less stable and areas or separate instances are needed

Unless you have no choice, avoid using special area types as they tend to create more problems than they solve.

4

OSPF areas came to be due to memory limitations. In modern networks you can push more routers and routes into an area.
Part of it depends on your overall design. In an ISP network you can put customer networks into their own area.