OSPF - ECMP to destination in Area 0

In most cases, ECMP will not be employed in OSPF if the destination can be reached via multiple areas. By definition, and when good practice and design is implemented, any routes found in one area should not typically be found in another area. Each area should advertise its own distinct networks.

However, load balancing can occur if you are trying to reach a network in Area 0 via two different non-backbone areas. So load balancing will only take place assuming that you are trying to reach networks outside of Areas two non-backbone areas.

Secondly, load balancing will only take place with OSPF if you have equal costs. When traversing different areas, the cost to reach a particular destination may be modified by the ABRs, so you must make sure that the cost is indeed equal.

Links

https://forum.networklessons.com/t/ospf-broadcast-network-type-over-frame-relay/918/30?u=lagapidis