单项选择题 Distribution layer: This layer includes LAN-based routers and layer 3 switches . When is a first-hop redundancy protocol needed in the distribution layer?（）

单项选择题 When dealing with transparent caching, where should the Content Engines be placed?（）

单项选择题 The VPN termination function provides the ability to connect two networks together securely over the internet. Which of these is true of IP addressing with regard to VPN termination?（）