By default, how is the best IGP path determined when there are multiple equal-cost paths to a destination?

When multiple equal-cost paths exist to a destination in an Interior Gateway Protocol (IGP) routing scenario, the method by which the router selects a best path can vary depending on the implementation of the routing protocol. However, in many cases, routers will choose among these equal-cost paths in a manner that is often random.

This random selection helps to distribute the traffic load evenly across the available paths, preventing any single path from becoming a bottleneck. This approach is particularly useful in scenarios where load balancing is necessary, as it allows the router to utilize all available equal-cost paths rather than favoring a specific one based on metrics like the order of learning or the highest next-hop IP address.

Routers may implement this random choice mechanism to enhance resilience and flexibility in routing, especially in larger, more complex networks. By doing so, they can optimize performance and ensure more efficient resource use across the network infrastructure.