Are there any practical disadvantages to making ALL OSPF non backbone areas some form of stub areas? It seems these areas only ever require default routes to the backbone, and never more.
This seems to only improve convergence, with no downsides. Why isn't this the default recommended architecture?
Stub areas cannot be used as a transit area for virtual links.
An ASBR cannot be internal to a stub area.
OSPF allows certain areas to be configured as stub areas, but the backbone area cannot be a stub area.
LSA Types 4 and 5 are not allowed in a stub area.
ref:
https://sourcedaddy.com/networking/stub-areas.html
Just to be clear, are these stub areas, totally stub areas, not so stubby areas, or totally not so stubby areas?
But, to the question at hand, if they're not needing to keep up with external routes from outside OSPF, then, stub 'em. Example: branch office that backhauls all traffic to the datacenter hub. Stub network, there.
There's no real reason not to just do NSSA just in case
With modern networks / CPU / RAM there really isn't a huge use-case (except for terrible WAN conditions etc.) for using lots of OSPF areas. A lot of ISPs will have 100+ routers in the same area lol