@Anthony-Sequeira Hi Anthony, thanks for your reply. I was taking Kevin's video on LSAs as the authority on the subject of stub areas and NSSA. In that video, he points out that the difference between a stub area and a NSSA is the presence of Type 7 LSAs. At least from his video Type 3 LSAs for internal networks and Type 3 LSAs for the default route are both still present in each area type.
The only reason I am digging into this is because I am a CCNA (route/switch), so only a basic knowledge of OSPF. That exam didn't really test or cover stub/nssa areas in detail. I used my CCNA studies to begin a dynamic route migration from all static in my organization. Currently we have about 30 routers in the environment (SonicWALL, not Cisco, so OSPF standards only apply). I've established our 4 core routers (beefier devices all with redundant circuits) as the area 0 backbone. The rest of the firewalls are smaller devices that may have 2 or 3 networks, but otherwise connect to area 0 to get everywhere else (except internet). The design basically looks like this...
I've converted probably 10 sites now and things are going well. One hiccup I ran into was an asymetric route problem with equal link costs, that got solved by manually adjusting costs so the paths were a bit more predictable. The SonicWALL firewall also has the ability to support asymetric routing, it was just something that had to be enabled on the interface. So covered on both fronts now.
I am just investigating sub areas to make sure that I am deploying this in the most efficient means possible. If I can reduce drag on the 4 core routers in Area 0 by using a stub area AND still accomplish my routing needs, I didn't want to find out about it after the project was completed. By the time this is all done, I am going to end up having about 25 or so OSPF areas for all of our tiny remote sites.
I am deploying these smaller sites into their own areas to prevent the Dijkstra convergence calculation across all routers in the org whenever there is a tunnel-interface failure to a remote site.. Which occurs frequently. I guess aside from the LSA differences described in Kevin's video, I don't really understand the benefit of the stub area. Especially if I can't use a default route to the ABR.
Thanks for your time.