传统的网络互连设备如网桥、路由器和交换机存在什么样的局限性？
参考答案：
网桥工作在数据链路层，网桥没有路由功能，无法实现流量控制，广播包的转发容易导致广播风暴，在某些情况下，因网桥拥塞而丢失帧，使得网络不稳定，不可靠。
路由器的功能主要是通过软件来实现的，处理延迟过高，容易成为网络“瓶颈”；路由器的复杂性还对网络的维护工作造成了沉重的负担。交换机工作在数据链路层，可以看作是对多端口桥扩展。交换机可以用来分割LAN，连接不同的LAN，或扩展LAN的覆盖范围。它同网桥一样，也不具有隔离广播包的能力。
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