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Re-subnet from /24 to /16

By rhino777 ·
I've been charged with heading up a re-subnetting of our network. Right now we're at a 10.x.x.x /24 type of setup. We have 25ish servers and half a dozen routers and many switches. We have almost 175 workstations consisting of about 25 actual desktops and the rest are Wyse thin clients. We want to move up to a 10.x.x.x /16 type of setup. We only have two guys that can do this kind of work. Are we better off just running around on a Saturday and manually changing all the systems and rebooting or is there an easier and/or more gradual approach that would make more sense?

Thanks for any help...

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dhcp

by gambo45 In reply to Re-subnet from /24 to /16

I would assume you guys are not running dhcp. If this is so that would be the first step. After you get that out of the way the subnet can be changed with a reboot of all your workstation.

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How is your DHCP setup?

by TomSal In reply to Re-subnet from /24 to /16

I'm assuming you are using DHCP. Do all the clients (desktips, thin clients) get their IP from DHCP?

Obviously you should have static IPs for the servers and the network gear.

You should do this after hours no matter how you do it - simply to make sure everything comes up smoothly, remember Murphy's Law...

However you can just change your addressing on DHCP (once you calculate what your scope(s) need to be of course) then release/renew the clients to pull the new addy.

All your static assignments will need manual entry.

I know it a pain, but when it comes to any kind of config/setting change that I'm doing to an entire network -- I rather let getting done faster take a back seat to getting done right the first time.

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My 2 cents:

by voldar In reply to How is your DHCP setup?

First of all, if you don't have a DHCP server - build one with the new settings of your future subnet. Use ping and arp -a to catch the MAC addresses of the computers with static adresses. Create in your new DHCP server the reservations for them.
Once you finished with the DHCP, start to switch the routers new netmasks (I assume you will keep the same IPs for them). Meanwhile, check on the technet site, you'll find a script that changes the static IP addresses to DHCP. Add this script to the logon script (machine settings). Don't forget to change any IP settings on the servers.
Restart all the computers after you changed the routers IP settings, and this should do your job! Everything done in less than 4 hours!

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Ouch

by voldar In reply to Re-subnet from /24 to /16

The first message should have been here. And .. where I said "netmask", you should read "subnet mask".
P.S. - sorry for my bad english, but I hope you got the picture.
Good luck!

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Modifying the existing scope's subnet mask?

by barth.travis In reply to Ouch

I want to change the subnet mask in the scope I have established on a Win Server 03 machine. It is grayed out, however. I need to go from 255.255.254.0 to 255.255.252.0

Please tell me that I don't have to recreate the entire scope!

Thanks.

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