采用可变长子网掩码VLSM技术可以把大的网络分成小的子网，例如把子网掩码为 255.255.0.0的网络40.15.0.0分为两个子网，假设第一个子网为40.15.0.0/17，则第二个子网为(28)。假设用户X1有2000台主机，则至少应给他分配(29)个C类网络，如果分配给用户X1的网络号为196.25.64.0，则指定给Xl的子网掩码为(30)；假设给用户X2分配的C类网络号为196.25.16.0～196.25.31.0，则X2的子网掩码应为(31)；如果路由器收到一个目标地址为11000100.00011001.01000011.00100001的数据报，则该数据报应送给(32)用户。

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(71) In the strength of the carrier signal is varied to represent binary 1 or 0.

  (72) is a system that can map a name to an address and conversely an address to an name.

  (73) is a three-way handshaking authentication protocol that it's packets are encapsulated in the point-to-point protocol

  (74) is an approach that enables an ATM Switch to behave like a LAN switch.

  (75) is an guided media which is made of glass or plastic and transmits signals in the form. of light.

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