当将相似的设备连接到另一个设备时，您可能想知道为什么使用一种特定类型的电缆而不是另一种。有鉴于此，今天的超级用户问答帖子回答了一位好奇读者的问题。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

照片由Dom Pates（Flickr）提供。

问题

超级用户读者user576476想知道为什么类似的设备使用交叉电缆而不是直通电缆：

Why do similar devices use a cross-over cable instead of a straight-through cable?

为什么类似的设备使用交叉电缆而不是直通电缆？

答案

超级用户贡献者Eric F为我们提供了答案：

Definition of a Cross-Over Cable

A cross-over cable is typically used between devices with the same type of interface (i.e. computer to computer, router to router). Ethernet cables are usually made as an A or B-type interface (which simply means how it is wired).

A cross-over cable simply has an A-type on one end and a B-type on the other end.

What is Happening

Basically, what is happening is that the “send” and “receive” are switched so that one of the devices “send” wires goes to the other device’s “receive” wire, and visa versa with the other wire. In reality, the wires are in pairs, so there are two wires for send and two wires for receive.

If you were to use a straight-through cable (where the wires are all-in-line), then a “send” would be going to a “send” and a “receive” to a “receive”, so the devices would not be able to communicate.

Auto MDI-X

Keep in mind that many modern devices use Auto MDI-X, which is a way for a device to automatically switch the wiring method on its own. If either device on the two ends of the Ethernet cable have Auto MDI-X, then it does not matter if you use a cross-over or straight-through cable. Auto MDI-X was introduced in Gigabit Ethernet, so if either of your devices uses Gigabit, such as routers or computers, it has an extremely high chance of having Auto MDI-X already on it.

有什么要补充的解释吗？在评论中发出声音。想从其他精通技术的Stack Exchange用户那里了解更多答案吗？在这里查看完整的讨论主题。