為什麼ISP會更改您的ip地址？

圖片由動態DNS服務提供商EasyDNS提供。...

If you rely on any sort of service that requires you to know the IP address of your home internet connection, there’s a good chance you’ve noticed that the number (however frequently or infrequently) changes. Why is that?

圖片由動態DNS服務提供商EasyDNS提供。

今天的問答環節是由SuperUser提供的，SuperUser是Stack Exchange的一個分支，是一個由社群驅動的問答網站分組。

問題

超級使用者讀者Agz很好奇為什麼他的ISP不給他一個固定的IP地址：

Is there any specific reason an ISP will need to change your IP address? What is the purpose of a dynamic IP versus a static IP? For me it seems to happen every 6 months, while for someone I know, it does once a week.

為什麼呢？為什麼不給每個顧客分配一個永久地址呢？

答案

SuperUser contributor Flimzy提供了對IP分配方法的一些見解：

When ISPs were first starting, everyone connected to the Internet over a modem. And most people used the Internet for a few minutes to a few hours per week. Assigning a static IP to every subscriber would have been very expensive, for something that most people used just a few minutes a week.

As broadband connecti*** have become more common, the practical reas*** for not assigning a static IP have become much less noticeable, as now the majority of connecti*** are “always-on”–even when nobody is (actively) using the Internet.

So there’s a bit of a historical reason not to use static IPs–customers are already accustomed to using dynamic IPs.

When modern ISPs enforce dynamic IPs these days, it may be in part to distinguish between “c***umer” and “professional” services–by reserving static IPs for customers who pay more, it gives customers who need that feature an incentive to upgrade their service level.

It can also serve as a deterrent for people abusing their c***umer-grade service. Many ISPs, for instance, explicitly prohibit running “servers” on a home Internet connection. If every home user had a static IP, they’d be more inclined to abuse such terms of service.

It’s also less of a management problem to assign customers dynamic IPs. If you move across town (but within the same ISP’s service area), there’s no need to re-assign how your static IP is routed; you’ll just get a dynamic IP that exists in the new neighborhood.

既然你知道為什麼你經常收到一個不同的IP地址，看看我們的文章如何輕鬆地訪問您的家庭網路從任何地方與DDNS配置您的家庭網路使用免費的動態DNS服務，輕鬆找到回家的路，無論多少次您的ISP改變您的IP。

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