How to deal with more than 256 devices on the same subnet



  • Hello,

    My company is a factory which using many tools with IP and computers to manage those tools. Right now, the overall number of ip devices approaching a full Class C subnet. And the need to separate them in two subnets became urgent.

    I know that ideally had to use VLANs but this will complicate the IP address management, as there is no physical separation.

    I am thinking two possible approaches and i want some advise about how to deal with it.

    i) to assign two separate subnets on the same physical interface. (Is it possible?)
    ii) to make the subnet /16 instead of /24. (Is there any consequence?)

    I would appreciate any help.

    Thanks in advance

    Stathis Alexopoulos



  • @stathis I'm not an expert ( so if you can try on a small architecture it would be better )

    1. You can make two different network on the same interface technically, but I don't really know how you can manage it (make a virtual interface with different parameters maybe).
      this imply if two of your devices plugged in the same switch, with different IPs, they won't communicate...

    2. I suggest you to extend the subnet. You can make the mask /23 (/16 will give you up to 65534 hosts : I'm not sure you need that much ...)
      you'll get 510 hosts with a mask at /23, is it enough ?
      To get it done, you need to update the mask on every host, I suggest you to a use DHCP server.

    Finally, you can handle VLANs but do you need to separate the networks ?
    VLAN is great if : you have multiple networks but a few host need to talk to other networks (like 1 network by floor but only one printer in the building). Otherwise they are another annoying task to handle (rules and stuff like this)

    Good luck with your problem !
    Max.D

    EDIT (02.12 11:05 GTM+1) : corrected error noticed by Rico


  • Rebel Alliance

    @maximedefrances said in How to deal with more than 256 devices on the same subnet:

    you'll get 5012 hosts with a mask at /23, is it enough ?

    /23 is 510 Hosts.

    -Rico



  • @rico Ho yes sorry, I wrote a too fast



  • Thanks a lot, for your help.

    I will try it with /23