Subnet Mask Change

[Grommit]

Hi

 

we need to expand our IP Address Range from 255.255.252.0 to ?

 

any advice or suggestions on how we can change all the fixed IP's onsite ? and Servers, AP, Printers, Onelans, Tills.. etc .. what is the next SN Mask up ?

 

Thanks

[Paid_Peanuts]

Just change the Subnet mask to 255.255.0.0

Thataway you will not need to change any ip addresses and you gain more

[timbo343]

It would be 255.255.251.0 but this wil only give you another x.1 ~ x.254 addresses but what Paid_peanuts said is probs the best way then you dont have to worry about running out of IPs

[ChrisH]

For windows servers with fixed IPs use a netsh script. For other devices use DHCP reservations and change their config accordingly. If they already have reservations delete them and remake.

Get a subnet calculator to see how many hosts etc to subnet ranges.

[Disease]

Why do you want to change the subnet mask? you can't have used all the available ips on a range unless you have a network the size of Microsofts?

 

Example here we use x.x.10.x for client ip's and to expand it by another 255 we just used x.x.11.x and to expand it further we could use x.x.12.x.

[zag]

Just change every device to 255.255.252.0, then extend your dhcp range. It should be pretty troublefree.

[Guest Guest]

Just change the Subnet mask to 255.255.0.0

Thatway you will not need to change any ip addresses and you gain more

 

Only if hes on a subnetted class A or B to start with, in which case he'd still need to change the subnet on every statically assigned device. Plus if hes on a subnetted class A/B chances are hes part of a wider network (ie RBC)

 

It would be 255.255.251.0

 

No its not. Its 255.255.248.0, there isnt such thing as a 251 subnet mask.

 

Why do you want to change the subnet mask? you can't have used all the available ips on a range unless you have a network the size of Microsofts?

 

What, MSs network has a whole 1022 hosts? Wow, alot!

 

 

 

Im not sure if theres an easy way of doing it tbh, would probably be best in a way anyhow as you will be able to plan all the scopes without concern for current ips.

 

Why did you have it subnetted in the first place? Are you part of a bigger network, like part of the council? If so then you cant just change your subnet, it wont work.

Cant really see any other reason to have a subnetted class A/B than if you are part of a bigger picture, so my bets are on you having to contact the council anyway.

 

 

If your network is just your own private one (no one else connected) i see no reason why not to go with a straight class B now ie 255.255.0.0 but you will still need to change your ips to a network with in this range 172.16.0.0 - 172.31.0.0

 

 

 

 

If you need anymore help give me a shout.

 

No offense to anyone else whos trying to help but if you arnt sure about what your talking about dont say it, as if he'd followed some of the advice on here he would have ended up with a dead network and im sure his boss(s) would have been happy with him when they came back after summer to find they have no computers and to get it fixed in a timely fation will cost x thousand £££

[Guest Guest]

I was having a think;

 

Give me ALL your details and i may have a solution for you, hopefully one which doesnt involve changing ip address's only the subnet.

[sparkeh]

Your subnet is the standard subnet for secondary schools (well certainly around here anyway) so looks like you could be part of a larger network, eg your RBC. Can you confirm whether this is true. If so then changing your subnet is a definite 'no go'.

 

Could you also confirm how many IP addresses you need. Your subnet will give you 1022 IPs. Have you really used all these 'cos thats a lot of stuff

 

EDIT: sorry to sparky for duplicating the things you posted :oops:

[webman]

10.0.0.0/255.0.0.0. Future-proof

[Guest Guest]

10.0.0.0/255.0.0.0. Future-proof

 

lmao

[Guest Guest]

Your subnet is the standard subnet for secondary schools (well certainly around here anyway) so looks like you could be part of a larger network, eg your RBC. Can you confirm whether this is true. If so then changing your subnet is a definite 'no go'.

 

Could you also confirm how many IP addresses you need. Your subnet will give you 1022 IPs. Have you really used all these 'cos thats a lot of stuff

 

EDIT: sorry to sparky for duplicating the things you posted :oops:

 

 

Its alright, ill let you off.

 

For a minute there i thought i was going mad as everyone had seemed to disagree with my way of thinking, good to know im still semi-sane

[Grommit]

I was having a think;

 

Give me ALL your details and i may have a solution for you, hopefully one which doesnt involve changing ip address's only the subnet.

 

Thanks for the input guys..

 

192.168.1.1 - 192.168.3.254

 

sn 255.255.252.0

 

and I am running out of IP addresses as I only have around 1024 IP addresses

 

And I need to go to 255.255.248.0 = 2048 Hosts

 

or 255.255.240.0 = 4096 hosts

 

I am not Sub Netted off of any other Network

 

My question was how do I expand the scope as I would have to change the SN mask and it would be OK on the PC's but on the static addresses I would have to manualy change the SN Mask which wuld be a bitch to do..

 

Any ideas :-)

[Guest Guest]

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 )

 

Personally id go straight to a private class b range now, you will need to change the subnet mask on all your devices anyway so you may aswell change the ip while your at it.

 

No theres no easy way of doing it on anything but PCs.

 

Yes it will work afaik but i suspect sooner or later you will find something which doesnt like having a private class c address with a class b mask.

 

If you go keep 192.168.x.x id just use 255.255.0.0, even if its just for th3e sake of typing less numbers lol

 

 

Can i ask why you/your school chose that class and mask in the first place

[sparkeh]

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

 

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

 

Can i ask why you/your school chose that class and mask in the first place

[Grommit]

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

 

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

 

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 ?

[doco]

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.

[Guest Guest]

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

[Guest Guest]

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

[Guest Guest]

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????

[sparkeh]

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.

[Guest Guest]

^ 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.

[webman]

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.

[DMcCoy]

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

[Guest Guest]

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