DHCP Question

Simple question ...

My DHCP server is running Windows 2003 R2. The subnet mask is 255.255.254.0, effectively giving me 510 IP addresses.

I am running out of IP addresses.

Can I change the subnet mask to 255.255.252.0, giving me 1022 IP addresses -WITHOUT- losing all of my reservations?

This is a simple, flat network here.

Thanks.
glenj1978Asked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

CorinTackNetwork EngineerCommented:
The closest you can get is exporting your reservations first, creating the new range, then importing them.

See the following article (and the first few comments) for how to accomplish this (the comments are necessary to understand what you need to do to get the reservations to import with the altered IP scope): http://koolbeans.wordpress.com/2007/07/31/howto-import-and-export-dhcp-reservations-in-server-2003/
0
Sandeep GuptaConsultantCommented:
since you are changing the subnet mask thus you have to flush all the existing with .254.

This is very simple change of not more than 5 minutes..with minimum impact
0
vivigattCommented:
Check this article:
http://support.microsoft.com/kb/255999

It does not mention how to keep your reservations, but check this article:
http://www.mpking.com/2013/08/using-netsh-to-export-and-import-dhcp.html

So now, a path is clear:
Use the netsh "dump" method described in the 2nd article to export your reservations

Extend your DHCP scope by resubnetting (use http://subnet-calculator.com if you need help with subnet ranges, starting and ending addresses etc) as described in the 1st artcile.

Import the DHCP reservations as described in the 2nd article.

Voilà !
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
glenj1978Author Commented:
Sandeep ...

I realize its a 2 minute change to change the subnet mask and instantly have 1022 IP addresses to give out, but I don't want to lose my 125 address reservations and have to re-enter them manually.

With all the millions of little utilities that have been written by everyone and their mother over the last 30 years, you'd think SOMEBODY would have written one that exports the reservations, changes the subnet mask, and imports the reservations back. Ugh :)
0
vivigattCommented:
The 2nd article I mention describes exactly how to export and import a list of DHCP reservations.
You will need to edit some text file but it should not be too complex.
If you can't figure it out, just run the command:
netsh dhcp server dump > dhcpcfg.txt

Open in new window

and attach the dhcpcfg.txt file to your reply, I'll create the modified text file for you and I'll let you know how to use it...
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Windows Networking

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.