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Wireless Networks Thread, Extending our current ip range in Technical; Hello all. Ive had a look through similar topics but still hitting a few problems so was wondering if I ...
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    dsk
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    Extending our current ip range

    Hello all. Ive had a look through similar topics but still hitting a few problems so was wondering if I could pick your lovely brains.

    We basically have two vlans and are currently running out of IP addresses (well actually we have more machine/devices) on our curriculum network and we're planning to make sure we have enough for around 2000 machines.

    Our curriculum subnet is 255.255.254.0/23 (class a) - 510 already maxed out.

    Our admin subnet also 255.255.254.0/23 (class a).

    Now im not sure if i understand this correctly, but considering we have two vlans to accomodate both networks (admi 10.64.90.xx range - curri 10.64.92.xx range) would there be problems if we just used a subnet of 255.255.248.0?

    Sorry if this seems very n00bish. Any help appreciated. Ta!

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    krb548's Avatar
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    Extending IP Range?

    Are you using Server 2003?
    I am also looking into this idea. We use a 255.255.252.0 subnet and have approx 1000 IP's to use but we are finding out that we are close to running out.

    I have been looking into super netting.
    From what I can see you can create a supernet and combine ranges together. I use 192.168.0.? - 192.168.3.255. I want to extend the range up to 192.168.9.255.

    I have also been struggling. Any ideas would be great, other wise I may have to do it the old fashioned way and change my subnet and re-build all my devices. That method seems a bit long winded.

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    dsk
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    haha, yes sorry, i should have said, we're currently on Sever 2003, non R2.

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    Are you doing the routing? or is it done externally?

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    dsk
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    Routing is all internally as far as i know (but im not too sure). Thanks!

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    You should find out, you're going to need to work with it.

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    In principle, there's no problem with extending the range. The problem comes with routing - something, somewhere, needs to know how to get back to your IP range.

    If all your machines connect to the internet via a proxy then I think the only thing you're going to have to change is the DHCP settings (easy) and then any systems with fixed IPs.

    If you have a default gateway that takes you out to the internet then the router will have to be adjusted so that it knows the new addresses are part of your range.

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    matt40k's Avatar
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    2000 machines?!? Nuts... DCSF\Becta reckon 2010 for 1:4 student\computer ratio (i think). 8000 kids? NOOOOOO the nightmare

    Who said to use admin range 10.64.90.0/23? They would be the first port of call of getting more IPs. Next step, how to do it.

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    FN-GM's Avatar
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    If you change your subnet mask 255.255.248.0 you will have 2048 addresses. If you want to allow more you can use 255.255.240.0 that will give you nearly 4100 addresses.

    This site may be helpful - Online IP Subnet Calculator

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    is there much of an overhead on using 255.255.0.0? what we use so we can give different rooms different subnets.

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    SYNACK's Avatar
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    Quote Originally Posted by browolf View Post
    is there much of an overhead on using 255.255.0.0? what we use so we can give different rooms different subnets.
    Depends on how many workstations you have using it. The main reason to subnet is to isolate broadcast frames which are sent to get things like DHCP, problem is that these are sent to every single machine on the network and so if you have enough machines the whole system will grind to a slow stop as it is inundated by croadcast frames. IP subnetting means that the broadcasts are isolated into that subnet as the router will not foward them.

    You can use that subnet easily but if you end up with too many hosts you man need to subnet back down again to keep the network stable and speedy.

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    Quote Originally Posted by browolf View Post
    is there much of an overhead on using 255.255.0.0? what we use so we can give different rooms different subnets.
    If you mean 192.168.1.x/16, 192.168.2.x/16, etc, these aren't different subnets, just logical (to a human) boundary points within one subnet. If your mask was /24 (255.255.255.0) then they would be.

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    Quote Originally Posted by SYNACK View Post
    Depends on how many workstations you have using it. The main reason to subnet is to isolate broadcast frames which are sent to get things like DHCP, problem is that these are sent to every single machine on the network and so if you have enough machines the whole system will grind to a slow stop as it is inundated by croadcast frames. IP subnetting means that the broadcasts are isolated into that subnet as the router will not foward them.

    You can use that subnet easily but if you end up with too many hosts you man need to subnet back down again to keep the network stable and speedy.
    we have in the region of 700 machines. all on 255.255.0.0, how many is too many?

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    Quote Originally Posted by browolf View Post
    we have in the region of 700 machines. all on 255.255.0.0, how many is too many?
    Depends on the systems that you are running and their usage patterns. Chuck wireshark on a pc and see how much of your traffic is broadcasts especially at the start of the day when everything is powered up. The other thing to remember is that a single faulty nic spewing broadcast frames will take down all of those hosts in one hit, if it was subnetted then the others would be isolated. Some switches now do have packet throtoling which alleviates the problem but will not solve it.

    I would probably be looking at 1000 as a high end margin for a school setup, not a wise one but one that is workable. Personally I prefer to keep my subnets down below 500 devices or even less given the usage pattern and hardware. I am lucky though to have cisco 3750 gear in the core at some schools which has layer 3 switching ability which effectivly removes the latency penalty and bandwidth constraints imposed by lesser routing methods.

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    dsk
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    Yep, all our machines connect to the net via proxy.

    Whos idea for the admin range? (the old manager - who didnt have much scope ).

    Ive tried deleting the scope and attempted to make a new one wit the subnnt of 255.255.248.0 (2048) which should suffice, but the range begins at 10.64.88.0 which would overlap the admin range (and where ai start to worry as its only separated by vlan).

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