In #3414 we removed the restrictions on using restricted IP ranges, but I think we should re-add the non-unicast ranges back. For example I don't think it's valid to use a multicast IP (224.0.0.0/4) or broadcast IP (255.255.255.255) as your interface IP address.

But it's unlikely that we'll support multicast or broadcast packets in Shadow any time soon, so I think restricting these IP ranges would be more to avoid confusion than something that would result in a bug.