You are designing a new Ethernet-based metro-area network for an enterprise customer to connect 50 sites within the same city OSPF will be the routing protocol used. The customer is primarily…

A multipoint Metro-E service (such as E-LAN or E-Tree) connects all 50 sites over a single shared Layer 2 domain, requiring only one IP subnet for all inter-router connections instead of a separate /30 subnet per point-to-point link - directly maximizing address conservation at scale.

Using /31 subnets or unnumbered interfaces reduces addressing slightly per link but still requires a subnet per P2P connection and does not scale as efficiently as a single multipoint subnet for 50 sites.

Designing OSPF in a hub-and-spoke topology using point-to-point logical links eliminates DR/BDR election on each segment, reducing adjacency formation overhead and significantly improving convergence time compared to full-mesh broadcast-type OSPF networks.

Address aggregation (route summarization) reduces routing table size and inter-area LSA flooding but does not conserve the interface addresses used on inter-router links themselves.

Explicitly determining DR/BDR roles is an operational step required when using OSPF broadcast network types, but it does not improve convergence - configuring P2P network types to avoid DR/BDR entirely is the preferred convergence optimization.