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Event ID 4321 Widows Server 2008 R2

We recently migrated to server 2008 R2 from SBS 2003, I noticed that the original network was using a subnet mask of but left it as it was. But now I see a post in EE that may explain the event id 4321 netbt errors that are constant. It suggests that the sM be changed to

Here is the layout of our server configuration:

Server 2008 R2   Domain Controller:          Using Hyper V on above server for two additiona servers:
          Server 2008 R2 / MS Exchange 2010
          Server 2008 R2 / Application Server

This error is only appearing on the Exchange Server.  What is the process to change all of these servers to the new Subnet mask ?   Top down? Bottom Up?  Reboots required? DHCP invoved I would assume.

Thank you in advance

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Assuming that all of the IP addresses have the same first 3 octets such as 192.168.1.XXX, you sould have no problem changing all of the subnet masks to It shouldn't matter the order that you do them in. Don't forget to change on the DHCP servers and all statically assigned devices, as well as the router. Update AD sites and services as well. I generally say that reboots should not be necessary, but they could be requested. It was Patch Tuesday this week, so if you didn't patch already this week now would be a good time. ;-)
jlspencerAuthor Commented:
So the order does not matter? I can do DHCP then the statics on the three servers?  What about the clients will they renew with out issue?  FYI all on same 3 octets, for the life of mme I do not know why the admin at set up the SBS 2003 opened it up to such a wide network.
Order should not matter, because the mask determines what the client thinks is part of the local network and what is remote. Everything that you actually talk to that you think is local will remain local, even with the new mask, so it's not a problem. I don't think that the clients will have any issue. I don't know if they need to go all to the to their lease expiring, or if they will get it at the next renewal period.
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