During a network design review, it is recommended that the network with a single large area should be broken up into a backbone and multiple nonbackbone areas. There are differing opinions on how…

There is a measurable impact because each additional ABR independently originates Type 3 LSAs, increasing LSDB size and flooding overhead.

SPF calculation complexity is determined by the number of nodes and links in the topology, not by how many ABRs exist per area.

In OSPF, each ABR generates a separate Type 3 Summary LSA for every inter-area prefix it advertises into the backbone and vice versa. Adding more ABRs per area means multiple routers each produce their own copies of these summaries and external route advertisements. This directly increases the total number of network summaries and external LSAs present in the LSDB across the domain.

The FIB may grow slightly as a downstream effect, but the primary and direct consequence of additional ABRs is on the LSA count and LSDB, not the FIB itself.