防火墙计算机要求2张以太网卡，一个对外部世界的接口和一个对主POP

The firewall machine will require two ethernet card, one interface to the outside world and one to the master pop network.

一种接口部件或电路，用来把数据转换成某种特殊的外围设备上的表示或某类外围设备上的表示或把此种表示转换成数据。例如，一台在串行位和并行位之间作转换且解决传输速度差别的设备。

An interface unit or circuitry that converts data to and from the representation used by a particular peripheral device or class of peripheral devices; for example, a device that converts between bit serial and bit parallel and resolves differences in transmission speeds.