I would like some advice regarding the design of an OSPF architecture. In particular, I would like to know when a new OSPF area should be specified, when a WAN link is included in the design. For example, at what WAN length, type, or speed should a new OSPF area be included?
actually the first important decision is:
to use a single area domain
to use multiple area domain
The second case requires the usage of OSPF area 0 as the central point for routing traffic and collecting routing info
The parameters to be taken in account are:
-number of routers
- number of ip prefixes
- level of control: using multiple areas allows for route aggregation and route filtering of internal routes at area boundaries on ABR nodes.
if the wan link is slow it is better to put it and the routers behind it in a totally stub area to minimize the OSPF DB and the info to be exchanged
Hope to help