How do I (Can I) expand scope in DHCP server to use all available IPs

windows-server-2008 networking ip

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You can use a single scope for all of those addresses, but according to this discussion you cannot expand an existing scope on MS DHCP, so you need to drop/delete it, and recreate it afresh.

However, if the scope is already that size, you do not need to drop or delete the scope. You can just change the start and end address for the assigned address range, as stated in the article linked by music2myear.

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music2myear

30-something guy who loves God, people, music, and computers, and happens to be reasonably good at the latter two. IT experience is nearly all self- and real-world-taught with no classroom and only a wee little bit of book learnin'. I'm driven by the dual motivations of being unable to leave well-enough alone and the desire to make technology work better for the user. My experience is mostly in Wintel systems administration and user support, with a smattering of *nix experience, mostly in the CLI, mostly on test machines and small-role systems, and I've acquired that experience in a wide range of professional business environments ranging from fast-food mega-conglomo-corps to international law firms to one of the largest corporate banks in the world, to small manufacturing firms and government departments.

Updated on September 18, 2022

Comments

music2myear almost 2 years
DHCP server: Server 2008 R2
IP info: 192.168.0.1/22
Subnet: 255.255.252.0
Gateway: 192.168.1.1

According to every calculator out there, 192.168.0.1/22 means I should be able to assign between 192.168.0.1 through 192.168.3.254 as I see fit. 192.168.0.0 being reserved for routing, and 192.168.3.255 for broadcast, leaving 1022 available addresses.

Currently we can only assign IP addresses between 192.168.1.1 and 192.168.2.254. Scope in our DHCP server has this limit, showing a starting address of 192.168.1.1 and an ending address of 192.168.2.254, allowing essentially only half of the addresses to be used.
- Can I change the scope to allow addressing of the rest of our calculated range?
- If so, how do I make this change of scope?
- Will I need to change the gateway address or can that remain at .1.1?
I would prefer to keep a single scope, if at all possible, keeping all the current exclusions and reservations.

UPDATE:

The main scope on the DHCP server already has the correct subnet (255.255.252.0, or /22). This means I'm not actually changing the subnet at all. I'm "simply" expanding the IP start and end addresses to what they ought to have been initially.

Reading this MS article it seems to answer my question: If I were changing the subnet or adding a new one, I'd have to create a new scope, or delete and recreate. However, since I'm only expanding my current start and end IP addresses to fill the existing subnets usable address space, the correct method should simply be to edit the properties of the scope.
- music2myear about 11 years
  
  Scope properties indicate subnet mask of 255.255.252.0 with a start IP of 192.168.1.1 and an end IP of 192.168.2.254. I believe, despite the limited start and end IPs, this indicates a /22.
NickW about 11 years

Read the bit about Resubnetting..
music2myear about 11 years

I've edited my question above to clarify. In short: I'm not changing my subnet, I'm "simply" changing the start and end IP addresses to fill the usable space of the existing subnet.
NickW about 11 years

Now you've put the question more clearly, I agree with you :) I'll change my answer to include that caveat.
music2myear about 11 years

Thank you for helping me clarify my own thinking. For a Network Administrator, I consider anything more than the physical aspects of networking to be my biggest weak spot in my IT knowledge.
Snellgrove about 11 years

It's so fiddly to extend sometimes, it's actually just easier to delete and recreate :-)
music2myear about 11 years

NickW, if you'd add an update to your response indicating the clarified question and correct answer, I'll happily give you the answer points.
NickW about 11 years

Cool, what else do I need to change?
music2myear about 11 years

That's perfect. Thanks for helping my mind shape itself around this problem today.