[单选题]OSI七层模型中,“包”是哪一层数据封装的名称()
                                                             正确答案 :C
                    
                      
                                                                                                                                                                                             网络层 
                                                                                                        
                    
                                     [单选题]On the topic of VLSM, which one of the following statements best describes the concept of the route aggregation?
                                                             正确答案 :B
                    
                      
                                                                                                                                         Combining routes to multiple networks into one supernet. 
                                                                                                                                                                                                                
                    解析:解析:Explanation: 
                                     [单选题]路由器上,命令“show int s0”的显示结果为:Serial0 is up,line protocol is down出现该结果的可能原因是()
                                                             正确答案 :C
                    
                      
                                                                                                                                                                                             两端设备协议不一致 
                                                                                                        
                    
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