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Bridgeman
25 pts.
 IP Addressing
DataCenter, Networking, Tech support
I have a network with a 255.255.255.128 Subnet mask inherited from a previous IT Manager. I am running short of IP Addresses and want to change the IP structure. If I leave the range of IP addresses alone but start changing the static IP addesses to a 255.255.255.0 subnet mask and then finally the DHCP addresses, Will this cause me communication problems during the transfer.

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ASKED: November 16, 2004  5:39 AM
UPDATED: December 25, 2004  8:36 PM
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Ideally it should NOT cause you any communication problems, if you keep using the same IP Address, and only change the mask. The problem will occure though, if you start assigning new addresses from the expanded range at the same time. I would recommend you to use an entirely new range, and configure a secondary IP Address on your router. This will ensure that there is no problems whatsoever during the changeover, since both the ranges (new and old) will be routed by your router during transition.
Last Wiki Answer Submitted:  November 16, 2004  7:02 am  by  Nandan   0 pts.
All Answer Wiki Contributors:  Nandan   0 pts.
To see all answers submitted to the Answer Wiki: View Answer History.


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I Agree with Nandan: leave the old range (and mask) unchanged. Start a new range (and mask) and add a route-entry for that range in all routing tables which are on the path. Start that with the DHCP scope (after you added the routing entry) will give you time to change the static entries one-by-one.
Only adjusting the mask will most likely cause communication problems since the route is not changed.
(an open door: when you are working in a team, communicate your planned change to prevent anyone still acting the old way).

Marchullegie
 0 pts.
 

What a coincidence.
Just had this happen to a client a few weeks ago.

Here’s what I did…
Early in the week set DHCP lease time to 1 day.
After-hours on Friday I changed the subnet mask on the DHCP and all static IP devices.
On Monday morning everything was working fine, DHCP renewed all leases with new subnet.

MrWizard
 0 pts.
 

In order for computers/servers to correctly see each other over the network they would need to be on the same subnet mask. If you begin changing the subnet mask on some, not all, those on the subnet 255.255.255.0 will communicate with each, and those 255.255.255.128 will communicate. You could use a route command to interface the 2, but if there are manageable number of computers to techs I suggest changing to the IP addresses scheme you prefer at one time.

Mable44
 0 pts.
 

check out learntosubnet.com for help

Jester42
 0 pts.