You have a network containing 120 routers. You must establish and maintain connectivity between the loopback interfaces of all routers. Because of the critical services using the network, you need red

OSPF (Open Shortest Path First) is a link-state routing protocol well-suited for large enterprise networks, offering fast convergence, hierarchical design (areas), and robust loop-free path calculation, making it ideal for redundancy and quick failover in a 120-router environment. It maintains a complete topology map, allowing it to quickly recalculate paths when a link fails.

RIP (Routing Information Protocol) is a distance-vector protocol that has slow convergence, limited hop count, and is generally unsuitable for large, critical networks requiring fast failover.

BGP (Border Gateway Protocol) is an Exterior Gateway Protocol primarily used for routing between autonomous systems (ASes) over the internet, not typically for internal routing within a single AS among 120 routers.

Static routing would be impractical to configure and maintain across 120 routers for full mesh loopback connectivity and would not provide fast, automatic failover without complex manual intervention.