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  • Question

  • Dear genius. You have just started as a server administrator for a small organization with a single location. The organization is using the 131.107.88.0/24 address range for the internal network. Is this a concern?
    • Edited by tenidaniels Saturday, July 25, 2020 11:41 PM
    Saturday, July 25, 2020 11:32 PM

All replies

  • Hi,

     

    Thanks for posting here.

     

    As we all know, the 131.108.88.0/24 address range is a public address range. If machines assigned with these IP do not need connect to the internet, then these IP address can be used for internal network. If these machines need to connect to the Internet, then it is not recommended to use an external range on your internal network.

     

    The use of a public range inside a private network is not a good design. While it will work, you will definately encounter issues if your internal users attempt to connect to an external resource such as a webserver on the internet within that range.  For example, let's say Google's webpage resolved to 128.1.1.1.  When an internal user attempts to connect to that page, the DNS client will first attempt to resolve the host name.  When the computer receives the DNS information, since the destination IP address is (from the computer's perspective) on the same network segment, the computer will NOT send the packet to the default gateway.  Instead, it will simply send out an ARP request for that IP.  If there is a computer with that IP on the local segment, it will respond.  Your computer will then attempt to connect to that other computer in the same segment to access the web page.  Of course, the web page will not appear for the user.

     

    The use of a public range inside your network does not automatically mean that packets will be able to get into your network.  For one, that IP range has not been assigned by your ISP to you so packets destined for that range would not reach your router.  However, a spoofed address can make its way in, assuming that you do not have a Firewall that checks for that.  In any case, its not a good design and it is not recommended to use an external range on your internal network.

     

    Please kindly refer to the following article for more information about Private and Public IP Addresses:

    https://wiki.teltonika-networks.com/view/Private_and_Public_IP_Addresses

    Please Note: Since the websites are not hosted by Microsoft, the links may change without notice. Microsoft does not guarantee the accuracy of this information.

     

    Please click “Mark as answer” if the reply is helpful. It would make this reply to the top and easier to be found for other people who has the similar problem.

     

    This "IPAM, DHCP, DNS" Forum will be migrating to a new home on Microsoft Q&A, please refer to this sticky post for more details.

     

    Best Regards,

    Sunny


    "IPAM, DHCP, DNS" forum will be migrating to a new home on Microsoft Q&A!

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    Monday, July 27, 2020 6:14 AM
  • Hi,

     

    Just checking in to see if the information provided was helpful. Please let us know if you would like further assistance.

     

    Best Regards,

    Sunny


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com   

    Wednesday, July 29, 2020 1:32 AM
  • Hi,

     

    Just want to confirm the current situations.

     

    Please feel free to let us know if you need further assistance.

     

    Best Regards,

    Sunny


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com   

    Thursday, July 30, 2020 9:54 AM
  • Hi,

     

    As this thread has been quiet for a while, we will propose the helpful reply as answer as the information provided should be helpful. If you need further help, please feel free to reply this post directly so we will be notified to follow it up.

     

    Best Regards,

    Sunny


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com   

    Monday, August 3, 2020 9:12 AM