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Windows Thread, Subnet Mask Change in Technical; Originally Posted by sparkeh Originally Posted by j17sparky Doesnt using a class b style subnetted private class c address confuse ...
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    Re: Subnet Mask Change

    Quote Originally Posted by sparkeh
    Quote Originally Posted by j17sparky
    Doesnt using a class b style subnetted private class c address confuse some apps/devices? (Sorry cant think of a better way of putting it )
    Well I have wondered this before but the RBCs hand out these subnets so I guess its ok (though I strongly suspect our RBC makes its decisions via magic eight-ball). However I work in the Primary phase where 254 IPs is ample so never tested it :P

    Quote Originally Posted by Grommit
    I am not Sub Netted off of any other Network
    So it looks like you are behind a server that hands out private address independent of the RBC? I will echo sparky's question about the choice of subnet - just interested really

    Quote Originally Posted by j17sparky
    Can i ask why you/your school chose that class and mask in the first place
    I Inherited it...

    What would you suggest the IP range and subnet mask to be ?

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    Re: Subnet Mask Change

    Like Grommit, I inherited our range, 192.168.0.x with a mask of 255.255.255.0. This was already set up and has a couple of addresses NAT'd through our firewall to the Segfl router, thence to Easynet's network. When we ran out of IPs, I changed this to 255.255.248.0 to give us more space. It works fine, the only problem I had was with two 3com WAPs which refused to accept the new mask, but a firmware upgrade to the latest 3com release solved it. It sounds like you have a similar setup, Grommit, so this may be a solution you can use.

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    Re: Subnet Mask Change

    THis is what im recommending to Grommit. If anyone can see fault with it please speak up.


    Network - 172.16.0.0/16 Which will give you a mask of 255.255.0.0

    The /16 above just refers to how much of the mask is the network, 16 mean the first 2 octets (255.255.) Just thought id put it in that form aswell incase you ever get asked.

    You will have over 65000 ip address' per network. Although you will never use that many theres no reason not to ie no real performance issues.

    So your range of usable ips will be 172.16.0.1 - 172.16.255.254


    This will give you great felxability in your scope; for example you could have
    Managed Switches and routers in this range - 172.16.1.0 - 172.16.1.255
    Servers in this range - 172.16.2.0 - 172.16.2.255
    Then an adiquate range for your clients (defined in DHCP), leaving spare for future development - ip cameras, video conferancing, media streaming etc etc.

    you dont have to devide it up like that, just make its more organised thats all.


    Should you need another network, for admin for example, just use 172.17.0.0 which will give you the same number of ip address' again. Its far easier to do it this way then to use variable lenght subnets.


    If any of that doesnt make sense just give us a shout.

    Sparky

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    Re: Subnet Mask Change

    BTW before doing this can i ask how do you connect to the internet? Via a private ISP ie BT, NTL etc?

    If its through the council you will still need to speak to them as if they use the same network address as you somewhere else in their network it could feck things up. For example;

    They may use the same private class B as their hub network for providing all schools with an IP address which is then NATed by you to your 192.168.x.x network.


    IF your connected by BT or anither private ISP you will be fine

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    Re: Subnet Mask Change

    Speaking to grommit he goes through the LEA. His forward facing ip address is in the 10. range, yet his private range is 192.168.


    Has anyone encountered this before? Just seems completely wrong to me. I dont believe for one second that his LEA/RBC has more than 1million schools to provide for (which would be the only reason to have a class A with private Cs for the schools, over a class B with private Cs)

    But in anycase if they have a class A scheme, why didnt they just allocate a subnet of that A to each school, like they have in my RBC????

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    Re: Subnet Mask Change

    Quote Originally Posted by j17sparky
    Speaking to grommit he goes through the LEA. His forward facing ip address is in the 10. range, yet his private range is 192.168.


    Has anyone encountered this before? Just seems completely wrong to me. I dont believe for one second that his LEA/RBC has more than 1million schools to provide for (which would be the only reason to have a class A with private Cs for the schools, over a class B with private Cs)

    But in anycase if they have a class A scheme, why didnt they just allocate a subnet of that A to each school, like they have in my RBC????
    The school I am at today works like this. Our server has the only RBC address that is used. Everything behind the server uses 192.168.0.0/24. This wasn't an RBC decision but the company who set the domain up. In fact it goes against the RBC standard network build which is a bit of a bind 'cos if there is ever any trouble they can trot out the 'well your network doesn't conform to the SNB so its your fault' excuse.

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    Re: Subnet Mask Change

    ^ Right.

    Well grommit id have a word with your LEA/RBC and see how you are supposed to set it up (assuming its like sparkehs case).

    We have the following setup;

    RBC set up a 10. network which stretches from past Newcastle to Middlesbrough (basically all of the northeast of england).
    They distribute ip ranges with a 255.255.240.0 mask (/20)
    My network is 10.64.128.0/20 range of - 10.64.128.0 - 10.64.143.255

    This means that any of the 4094 ip address's in my range can have direct access to the internet via the RBCs exterior firewall, or direct access to any device on the NGfL (northeast network). No natting goes on anywhere on my network, only (afaik) near the pipe out to the internet.

    My first suspisions when i first read your post were that you had it set up wrong*, you will have to confirm whether or not your LEA/RBC have a set way of doing things or not.

    *Not that its your fault as you inherited it.

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    Re: Subnet Mask Change

    The NGfL doesn't cover Durham though, we're a completely different kettle of fish The IP security method would probably work as expected with all schools using DurhamNET - we each have our own external IP address on the internet. However we do go through their central proxy server so it depends on how the website detects the IP address.

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    Re: Subnet Mask Change

    I don't use the RBC assigned ranges, I don't see why I would want to use them. Only things like the proxy and firewall have ip addresses in the range to provide internet access.

    I'm currently on a 10.0.0.1-10.0.7.255 255.255.248.0 subnet, but I'm moving to setup with /24 subnets with vlans and inter-vlan routing.

    The LA have virtually no influence on the IT here, even before I started and apart from the internet connection we do what we want. The sims server has always been ours for example.

    I prefer 10.0.X.X IP ranges due to it being faster to type and a more pleasing number arrangment

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    Re: Subnet Mask Change

    Good reason

    Our LEA/RBC have alot of say in what we do. We have viedo conferancing kit which will not work unless we use our provided scheme or are allowed access to our router in order to configure PAT/NAT. Neither of which is going to happen.
    The video conferancing was originally planned to be inter-school, using the *very costly* (almost) direct links between schools. Never happened though and now we go via a gateway which completely defeats the point of the network.


    Forgot about durham, god you lucky so and so's. I wish i had control over my own affairs. I remember talking to you about remote access and that you use a WebDav method, which was easily implimented as you only had to ask Durhamnet for a public IP to be forwarded and it happened.

    We on the other hand have been demanding remote access for 3years now and afaik we are no closer to getting it. All we get is "oh we're trailing it now, its going good. Soon..."
    And it never materialises

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    Re: Subnet Mask Change

    Quote Originally Posted by j17sparky
    We on the other hand have been demanding remote access for 3years now and afaik we are no closer to getting it. All we get is "oh we're trailing it now, its going good. Soon..."
    And it never materialises
    *Ouch*
    I should have remote access setup over the hols, as critical as I am about our RBC, I just just asked for an external IP and a dns record change it was done the same day.

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    Quote Originally Posted by ChrisH View Post
    For windows servers with fixed IPs use a netsh script.
    All our machines here are static ip addressed, and now we need to change just the subnet mask to 255.255.0.0 on them all.

    How can I use netsh to change just the subnet mask and keep the machine IP?

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