Increase the size od DHCP Scope

I am using Windows 2003 as a DNS adn DHCP server. I am running out of Ip addresses. I am using 192.168.0.1  - 255 with a sub net of 255.255.255.0  I want to change the sub net to 255.255.254.0  Do i have to delete my existing scope to do this - and what about the reservations that I have already assigned - will I loose these?
jontyplattAsked:
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sathaihostCommented:
i think the 192.168.x.x range is max out at 255 per scope. therefore if you are going to link 192.168.0.x to 192.168.1.x you must route them together with a router.

for your option is to get another NIC and put it on your currect Win 2003 server box and route the to network together and that the DHCP could broadcast IP to both subnet.  

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lost_enigmaVP of IT infrastructureCommented:
Yes, you can delete a scope, clients will update there addresses.
BUT. this may cause a problem, because you have to change address of the server also.
We do this before, but sometimes you can face with a problems with DHCP when change address of server.

I would also recommend to use additional equipment and create another subnet (or additional network card, as sathaihist said).
Chev_PCNCommented:
Changing your subnet mask will require re-assigning addresses to every single DHCP client on that subnet.
It will also affect your routers (if any), which will need to be reconfigured, managed switches (if any), all servers, NW-attached printers, etc, etc.
192.168.0.111 / 255.255.255.0 and 192.168.0.111 / 255.255.254.0 are on two completely different subnets.
My suggestion would be:
If your switches are capable, then add another VLAN, (use a L3 switch to do the routing or add a router) and add a completely seperate scope on your server, e.g. 192.168.1.x.
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scadieuxCommented:
What i would do is reduce the lease time to 24 hours, wait for a friday night and delete your scope and create a new one with the 255.255.254.0 subnet mask. I've done that several times and it'll work without your users noticing.
jontyplattAuthor Commented:
Thanks for all of this - but actually no one has answered the question. Do I have to delete my existing scope and will I have to loose all the reservations I have created?
scadieuxCommented:
Yes you need to delete the scope. As for the reservations,
You can export and import them using the netsh command.

http://koolbeans.wordpress.com/2007/07/31/howto-import-and-export-dhcp-reservations-in-server-2003/
sathaihostCommented:
No, you don't have to delete your existing scope because you can route the 2 subnet together with your routing unit. Therefore, what you have done will not need to be modified at all.

i hope this answer your question.
Krzysztof PytkoSenior Active Directory EngineerCommented:
Hi,

do we speak about Windows Server DHCP ? If so, unfortunately, you have to delete scope, because Windows DHCP doesn't allow subnet mask change.

In this case the most appropriate option for you is to create another scope on DHCP server and then create "Super Scope" linking 2 or more scopes on that server to be present as one scope.

Regards,
Krzysztof
Krzysztof PytkoSenior Active Directory EngineerCommented:
OK , we speak about Windows DHCP server :]
lost_enigmaVP of IT infrastructureCommented:
If you decide to change scope (change mask) then you have to recreate all reservations, because they was created for other subnet and scope.

So you can think about second variant with several subnets and routing between them
jontyplattAuthor Commented:
So if I have a router will I just have one DHCP server with two scopes?

Surley the easiest way of handling this is witha  superscope?
lost_enigmaVP of IT infrastructureCommented:
router or second network card

about superscope wait for his reply.. i do not use it before
Chev_PCNCommented:
In this instance a superscope is not an option as you still need to change the subnet mask (and therefore delete the original scope.)
A superscope is used to "group multiple scopes as a single administrative entity."
See : http://technet.microsoft.com/en-us/library/cc757614%28WS.10%29.aspx
Also:  http://technet.microsoft.com/en-us/library/cc958938.aspx

*NB* your router must allow DHCP broadcasts - you will most probably need to enable IP_Helper.
http://support.microsoft.com/kb/257579
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