NEW IP RANGE

[z4ydi]

Our ISP has changed our IP range for curriculum network so that we can accomodate more clients on the network as the old range only allowed 254 hosts (Old IP settings: 10.8.100.0 subnet mask 255.255.255.0/24) which gives us 254 hosts.
on the new range they have changed our IP address to 10.8.101.0 with a subnet mask of 225.255.252.0/22 which will allow 1022 hosts."
please guide me step by step how to configure my DHCP and DNS for the new IP range.

[StewartKnight]

This is incredibly simple to do
Look at this website for a detailed guide.

[z4ydi]

I traied to edit the existing scope but i can not edit the subnet mask, it is grayed out for some reasons. any clues?

[strawberry]

i dont think you can edit a subnet mask, i beleive you have to recreate the scope.

[User3204]

Are you sure that that is the right IP range ?

The range 10.8.101.0/22 isn't right, I expect the range has changed to 10.8.100.0/22, which will encompass the old range and the new range from 10.8.100.0 to 10.8.103.255.

So you can keep using the old range for a while.

Unless they've changed Windows you will have to create a new DHCP scope.
Basically:

1. change the subnet masks on the servers to handle the new 255.255.252.0;
2. create a new scope in the DHCP server, but leave it disabled. Copy the details from the existing scope;
3. change the existing scope lease time to 4 hours or something short;
4. at the end of one day disable the old scope, and enable the new one;
5. wait for next day, and hopefully noone screams;

[z4ydi]

Are you sure that that is the right IP range ?

The range 10.8.101.0/22 isn't right, I expect the range has changed to 10.8.100.0/22, which will encompass the old range and the new range from 10.8.100.0 to 10.8.103.255.

So you can keep using the old range for a while.

Unless they've changed Windows you will have to create a new DHCP scope.
Basically:

1. change the subnet masks on the servers to handle the new 255.255.252.0;
2. create a new scope in the DHCP server, but leave it disabled. Copy the details from the existing scope;
3. change the existing scope lease time to 4 hours or something short;
4. at the end of one day disable the old scope, and enable the new one;
5. wait for next day, and hopefully noone screams;

I realised the error and I called our ISP and asked them to only change the subnet maske from 255.255.255.0; to 255.255.252.0 and leave the ip address s 10.8.100.0 they have realised thier mistake and changed the ip back to 10.8.100.0. Now I tried to create a new scope it comes up with an error message saying "this is a wrong scope or the scope already exists" though this is not the exact wording of the error but it is something in the same line. I disabled the existing scope and then tried to create a new one it still did not allow me.

[User3204]

Bugger,

I have only ever changed scopes from one range to a completely different range (10.10.y.z went to 10.0.y.z etc) and this works, I kinda assumed it would work. But I expect overlapping ranges on the same server ain't something anyone should do.

Do you have another server you could setup as a DHCP ? DHCP doesn't take up a lot of processor on the server, try another DC.

If not, you will have to delete the original range to create the new one.

Sorry.

I have two DHCP servers that can give out IP addresses in the same range, it's setup for redundancy, supposedly.