it's not possible to directly change the subnet mask of an existing DHCP scope in a running Windows DHCP server.
Here are the steps:
1. Export the Existing Scope Configuration:
Open a command prompt with administrative privileges.
Type the following command to export the scope configuration to a text file:
netsh dhcp server \\<DHCP_Server_Name> scope <Scope_IP_Address> dump > C:\dhcp.txt
2. Modify the Configuration File:
- Open the dhcp.txt file in a text editor.
- Locate the line that specifies the subnet mask (e.g., SubnetMask 255.255.255.0).
- Change the subnet mask to the desired value.
- Save the changes to the file.
3. Delete the Old Scope:
- In the DHCP management console, right-click the scope you want to modify and select "Delete."
4. Import the New Scope:
5. Verify the Changes:
- In the DHCP management console, check if the scope has been re-created with the new subnet mask.
- Right-click the scope and select "Properties" to confirm the subnet mask change.
(Major Point - Ensure that your existing network address and subnet network address remain the same after making changes. If they are not the same, you need to modify the entire network address in the text file. For example, if the original subnet is 255.255.255.0 and the network address is 10.1.10.0, and you change it to 255.255.252.0, then the network address should also be updated to 10.1.8.0. Therefore, you must replace all instances of 10.1.10.0 with 10.1.8.0 in the entire text file (using Ctrl+H for the replacement).
Thats it....
