Too many IPs on subnet

Posted on 2011-05-06
Last Modified: 2012-05-11
Hardware/software used:   Windows Server 2008 Ent R2.  HP procurve switches (1800).

I am at the point where my network at work is starting to have too many devices that are requesting for IPs from DHCP server (windows server 2008 R2).  Due to the cabling, I can't really place a router for a different segment of the building, and also would rather not separate them such that I can't directly reach the client computer from the server if I need to login remotely (without setting up more port-forwarding on a new router for that segment).

What I thought of doing was to define two scopes for IPs  ( to  and to allowing 400 devices on the network.  My servers are on 10.0.1.x, and various devices have static IPs which is why I am not giving out IPs from x.x.x.1 to x.x.x.254.  If I keep my current scope as it is (due to servers/printers/etc), not give out any dynamic IPs on 10.0.1.x, but rather create the two scopes mentioned above on the same server to give out dynamic IPs within a certain range, should everything be able to communicate as before?  Will the dynamic IPs handed out be random from each of the two scopes that have the dynamic range assigned?   I was also wondering if I had some HP1800 procurves, if it would be simple enough to have all devices past the point of that switch be assigned IPs from the second scope as opposed to the first scope?
Question by:metazend
    LVL 12

    Accepted Solution

    Why dont you use the
    IPs 10.10.X.X and subnet

    That would give  you a large scope of IP address.

    The only thing is you will have to reconfigure the subnet
    manually for the static IPs. You will also have to change the subnet
    mask of your DHCP servers.

    LVL 26

    Assisted Solution

    You can use a /23 mask that will double your typical /24 network.  For example  would have a range of - These would all be on the same network. So your subnet mask would be
    LVL 12

    Assisted Solution

    I agree with Soulja, go with a smaller mask but don't go do a fully class B mask.  That could hamper you years down the road when your company buys another, or merges with someone or partners with someone...... You need to keep flexible.

    I use a smidge bigger at our largest site which has about 300 users + servers and printers and everything
    I use /22 giving you 1022 hosts for the subnet -

    but regardless, just increase your mask, change the mask on all your devices, DHCP, servers, switches, routers, printers, etc and you'll be good to go

    Author Comment

    Hi guys,

    I tested various situations, and I think all your solutions are really great.  I've ended up using asidu's solution because of the simplicity, and that I may also have to a larger subnet later.  I was also unsure of how to get some systems to communicate with each other using /22 or the like.

    For instance, with as the subnet mask, I can make two systems on different subnets communicate (i.e.  10.0.10.x and 10.0.11.x) but I wasn't sure if they two subnets need to be consecutive numbers such as x.x.10.x and x.x.11.x or if it could be anything.   Using relieved the headaches a bit!   Although, if someone could quickly clarify, that would be fantastic.

    Thanks again.
    LVL 12

    Expert Comment


    Have a look at the subnet mask calculator and the scope of IP which you can
    get for your designed network.

    You can vary the input of your network, select various netmask to see the ranges of subnet that
    could be made available to you.
    Answer to your question of two subnets ...they should be consecutive.
    I am not able to explain the theory and details thou...results can be checked by using the

    If you are on a private network, the easiest solution for future expansions is to use class B with
    a mask of
    You will have more than enough subnets for your needs.

    Hope that helps.

    Good luck :)


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