[SOLVED] public IP in local network gost?

[johnyb98]

Hello everybody.

Please, I would like your help to make things clear in something I saw about networking.

In specific video (this is part 2/3), he turns auto to a static IP address.
But, as you can see, the static IP he gives locally to the ethernet interface is 199.207.13.45.
How is it possible? As far as I know and read (and here is something I misunderstand), in local networks, you can give a Class A/B/C IPv4 address to an ethernet interface.
199.x.x.x is out of this ranges. 199.x.x.x are refered to public IPs.

How is it possible to give 199.207.13.45 (network 199.207.13.x - subnet: 255.255.255.0 as he says), and this works?

Thank you for your time!

 

[bill001g]

There is no rule that says you can only use certain blocks on your internal network. If you are big company like microsoft that has many blocks of ip they assign public ip to many of there internal machines. Lot of big companies that got huge blocks of ip when the internet was new also use them for internal use. Many times these are not advertised on the internet or if they are they are set to a dummy route to discard the traffic.

Even if you don't have ip addresses assigned you there is nothing stopping you from using anything you want. The only risk is that if you for example duplicate the ip used for some web site you would not have any access to it. I know some companies use the blocks allocated to things like the department of defense since these are not on the internet and you would not ever have access to them anyway.

Part of your confusion maybe that some consumer router have restrictions on what they let you key in. Mostly this is to protect consumers who don't want to spend the time to learn what private and public ips are.

 

[johnyb98]

Thank you very much for your time and for your all writting extremely answer!!

I am totally sorry for my insist on my question but I still do not understand something. You say in your answer:

Even if you don't have ip addresses assigned you there is nothing stopping you from using anything you want.

At the moment, I do not have a Windows PC to try it but I believe that if I tried in a e.g. Windows 7 machine give a static IPv4 199.207.13.45/24 I would get error message stopping me. What is your opinion on this?

 

[bill001g]

It should work. Lets say the company that owns that IP block wanted to assign it to their machines. Why would there by any limitations. There is no way for microsoft to know who owns a machine and somehow restrict it to certain ip blocks.

There are small blocks of ip that are defined for things like multicast or loopback etc that might be blocked but normal public IP won't.

They reason it does not hurt anything is even if you have a commercial internet connection the ISP will prevent you from advertising any networks you do not own into the BGP routing tables. You can use them all you want internally but you will be blocked by the ISP from adverting them into the internet. This is to prevent IP block theft.

 

[johnyb98]

Awesome answer and many thanks.

So, here is the key of the solutionublic IP (or public IP subnet) leased/bought from ISP. If someone has bought an ISP public IP, there is no prevention of using it in a local segment resource. So, the guy in video, is using this IP (199.207.13.45/24 ) that has bought from an ISP.

Now, everything understood and many thanks!!