Replace MapEntry with a POD
Currently the Map class used in the RoutingTable maintains a collection of MapEntry objects. However, these objects are only used within Map, and MapEntry only serves to aggregate two values. This collection is essentially a POD, and separating it into its own class suggests that it should have some behavior of its own. Since it doesn't, this could be considered confusing. It also slows down compile times and damages readability, by adding complexity in an entirely unnecessary way.
Instead, this could be represented with a const tuple or a const struct, since the class as-implemented wants to be immutable. Re-implementing it as a POD would save almost 100 LOC, prevent an include, and ease readability.