在分级设计模型中，通常把网络设计分为3层，即核心层、汇聚层和接入层。下图所示的是某公司的网络拓扑图，但该公司采用的是紧缩核心模型，即将核心层和汇聚层由同一交换机来完成。 公司网络中的设备或系统（包括：存储商业机密的数据库服务器、邮件服务器，存储资源代码的PC机、应用网关、存储私人信息的PC...
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