IP地址以零结尾？ [英] IP-address ending with zero?

问题描述

这可能不是正确的地方或正确的时间，但我有一个问题。
我是一名计算机工程师，我知道一些关于网络的事情，但是当我看到（见图）时，我已经WTF了。

This might not be the right place or the right time, but I have a question. I'm a computer-engineer and I know a few things about networking, but when I saw (see pic), I WTF'ed.

情况：
本周五我回到家，被要求帮助我父亲解决一些网络问题。他不久前坐了几台IP摄像机，我从任何地方都可以使用它。但本周IPS做了某种重启或升级或者什么，我们得到了图片上显示的IP。
现在我无法从外部IP连接到这些IP摄像头。

Situation: I came home this Friday and was asked to help my dad with some network-problems. He sat up a few IP-Cameras a while ago, and I got it working from anywhere. But this week the IPS did some sort of "Reboot" or upgrade or what ever, and we got the IP shown on the picture. Now I'm not able to connect to these IP-Cams from an external IP.

假设：
我猜这个IPS坐着一个少于24位的子网掩码，但IPS为什么要这样做呢？
为什么我无法连接到这个IP？

Hypothesis: I'm guessing the IPS sat a subnet-mask with less than 24bits, but why would a IPS want to do this? And how come I can't connect to this IP?

任何人都有什么可说的情况？
如果我只是联系IPS，我很可能会得到一个新的IP，但我想我只是为了好玩而分享这个。我从没想过会从IPS获得这样的IP：p

Anyone have anything to say about the situation? I will most likely get a new IP if I just contact the IPS, but I thought I'd share this just for fun. I never expected to get such IP from an IPS :p

推荐答案

以结尾的IP地址.0 这些天完全合法。但是，某些设备（和防火墙策略）认为它不是。

An IP address ending in .0 is perfectly legal these days. However, some devices (and firewall policies) believe that it isn't.

在旧的classfull寻址方案中，IP从192.0 .0.0到223.255.255.255被认为是C类空间，即它们的隐含子网掩码为255.255.255.0。

In the old "classfull" addressing scheme, IPs from 192.0.0.0 to 223.255.255.255 were considered "class C" space, i.e. they had an implicit subnet mask of 255.255.255.0.

所以，那时候，你不能实际上有 .0 主机地址，因为 .0 是网络地址。同样，你不能在该范围内拥有 .255 地址，因为这是广播地址。

So, back then, you couldn't actually have a .0 host address, because .0 was the "network address". Similarly you couldn't have a .255 address within that range because that was the broadcast address.

约20但是，几年前，每个人都改为无类别CIDR样式寻址，具有可变长度的子网掩码，并且没有隐式子网掩码。如果你有一个 / 23 那么你就不应该有任何理由不能使用 .255 那是在第一个 / 24 的末尾和 .0 那是在下一个开始时。

About 20 years ago, though, everyone changed to "classless" CIDR style addressing, with variable length subnet masks, and no implicit subnet masks. If you've got a /23 then there shouldn't be any reason why you can't use the .255 that's at the end of the first /24 and the .0 that's at the start of the next.

然而，5年多以前，当我在ISP行业时，我们的系统很乐意发出 .0 和 .255 最终用户的地址，但后来我们发现他们无法访问微软的网站，因为他们有破坏套件或过度热心的防火墙规则。我们最终不得不排除这些地址，即使它们是合法的。

However, 5+ years ago when I was in the ISP industry our system would happily give out .0 and .255 addresses to end users, but then we found that they couldn't reach Microsoft's websites because they had either broken kit, or overzealous firewall rules. We ended up having to exclude those addresses, even though they're legal.

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