网络交换器（英语：Network switch）是一个扩大网络的器材，能为子网络中提供更多的连接端口，以便连接更多的电脑。

二层交换机工作于OSI参考模型的第二层，即数据链路层。交换机内部的CPU会在每个端口成功连接时，通过将MAC地址和端口对应，形成一张MAC表。在今后的通讯中，发往该MAC地址的数据包将仅送往其对应的端口，而不是所有的端口。因此，交换机可用于划分数据链路层广播，即冲突域；但它不能划分网络层广播，即广播域。

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通常，交换机采取直通转发，如果误码率上升到某个阈值，再改用存储转发。

A network switch (also called switching hub, bridging hub, officially MAC bridge) is a computer networking device that connects devices together on a computer network, by using packet switching to receive, process and forward data to the destination device. Unlike less advanced network hubs, a network switch forwards data only to one or multiple devices that need to receive it, rather than broadcasting the same data out of each of its ports.