https://azure.microsoft.com/en-us/documentation/articles/expressroute-premium-sku/
ExpressRoute Premium add-on によって、拡張される部分は以下の3点
■リンクできるvNetの数が増える
どれくらい増やせるか、はココ
•Increased number of virtual networks (VNets) that can be connected to the ExpressRoute circuit (default is 10).
■異なる大陸のvNetにもリンクできる
•Global connectivity over the Microsoft core network. You will now be able to link a VNet in one geopolitical region with an ExpressRoute circuit in another region. Example: You can link a VNet created in Europe West to an ExpressRoute circuit created in Silicon Valley.
4000でも十分大きめの上限ですが、さらに。
•Increased routing table limit from 4000 routes to 10,000 routes for public peering and private peering.
