DHCP: Create a scope within a scope
Before I joined the company I am currently working for, they set up a scope to encompass the 10.2.0.0/18 range of IP addresses (10.2.0.0-10.2.63.254).
I was recently tasked with adding reservations to DHCP so that the entire 10.2.26.0/8 (10.2.26.0-10.2.26.255) range cannot be distributed or assigned.
The first thing I thought about was to create a scope with this range of IPs, but then it occurred to me that this would conflict with the current scope that was already defined.
Is there a way to create a "scope within a scope" or a similar method so that I can effectively prohibit IPs in the 10.2.26.0/8 (10.2.26.0-10.2.26.255) range from being assigned or reserved?
Ip addresses are meaningless without a subnet mask. When you say the scope encompasses the whole 10.2.0.0 range and then say that range is 10.2.0.0-10.2.63.254 you're implying a subnet mask of /18 (255.255.192.0) because that's the only subnet mask that gives you that ip address range, but we wouldn't know that is the subnet mask you're using because you didn't state what the subnet mask is for your range/scope. Saying it encompasses the "whole" range is incorrect because the "whole" range would be 10.2.0.0/16 (255.255.0.0) encompassing the ip address range 10.2.0.0-10.2.255.255.
You need to configure exclusions, not reservations and you definitely don't need to configure a "scope within a scope", whatever that is.
A reservation ties an ip address to a MAC address. It ensures that the host with that MAC address will always be assigned that ip address by DHCP. The caveat is that the host needs to be configured to acquire it's ip address via DHCP.
An exclusion tells the DHCP server to never assign that ip address (or addresses) to a DHCP client. This leaves that ip address (or addresses) available to you to manually assign to hosts.