I have these classes

public class EntityBase : IEntity
{
    public int Id { get; set; }
    public DateTime Created { get; set; }
    public string CreatedBy { get; set; }
    public DateTime Updated { get; set; }
    public string UpdatedBy { get; set; } 
}

public class EftInterface : EntityBase
{
    public string Name { get; set; }
    public Provider Provider { get; set; }
    public List<BusinessUnit> BusinessUnits { get; set; }       
}

public class Provider : EntityBase, IEntity
{
    public string Name { get; set; }
    public decimal DefaultDebitLimit { get; set; }
    public decimal DefaultCreditLimit { get; set; }
    public decimal TreasuryDebitLimit { get; set; }
    public decimal TreasuryCreditLimit { get; set; }
}

public class BusinessUnit : EntityBase
{
    public string Name { get; set; }
}

An interface, is really a Provider, with a collection of Business Units. The issue is that while my db model ends up having a correct EftInterfaces table, with a FK to Provider_Id, the BusinessUnits table has a FK to EftInterface_Id.

But, a BusinessUnit can be included in more than one EftInterface.

I need a many to many relationship. A BusinessUnit can be part of many EftInterfaces, and an EftInterface can contain many BusinessUnits.

How can I get CodeFirst to generate the many-to-many table?