# [SOLVED] Changing Subnet Mask



## shoota_nz (Sep 5, 2010)

I'm the IT manager for a school and I'm trying to impliment a new server into an exisiting network. While installing Server 2008 stn. I used the standard 255.0.0.0 subnet mask but because it would be a big undertaking to change all existing static ip addresses (copiers, routers, proxy, access points , controllers who have the 255.255.255.0 subnet I've decided to change the server to 255.255.255.0. After changing the NIC and deleting the DHCP and DNS servers and reconfigured with out success. I've manually edited the registry, where I found two entries with 255.0.0.0. After rebooting the DHCP is still sending the wrong subnet. 

I don't want to reinstall the server as I've setup all the user accounts etc before finding the problem with the incorrect subnet. Can someone help please as I've spent a day searching the internet on how to fix this small issue.

Thanks for your help from a frustrated dummy IT manager


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## BlueEyedSamurai (Aug 4, 2008)

*Re: Changing Subnet Mask*

Shoota - on the new W2K8 server, you should only have to enter the static IP address into the IPv4 properties. Even if you initially assigned it a subnet mask of 255.0.0.0. Enter in the static IPv4 address, subnet mask, gateway, and DNS server(s). As long as this server is connected to the same network, changing the subnet shouldn't matter.

What aren't you able to connect with? Can you do an ipconfig/all and copy and paste the results into your next post so we can take a look?

-Samurai


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## mjfinca (Aug 19, 2010)

*Re: Changing Subnet Mask*

If you're saying that the DHCP server is supplying the wrong subnet mask, you'll need to change the setting in the DHCP console.


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## grutz (Jun 5, 2008)

*Re: Changing Subnet Mask*

I'd love to change the subnet in DHCP console but cannot find it.


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## grutz (Jun 5, 2008)

*Re: Changing Subnet Mask*

Server IPconfig /all

Microsoft Windows [Version 6.0.6002]
Copyright (c) 2006 Microsoft Corporation. All rights reserved.

C:\Users\Administrator>ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . : Server3
Primary Dns Suffix . . . . . . . : levin.school
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : levin.school

Ethernet adapter Local Area Connection 2:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek RTL8168C(P)/8111C(P) Family PCI-E
Gigabit Ethernet NIC (NDIS 6.0)
Physical Address. . . . . . . . . : E0-CB-4E-AB-26-85
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek RTL8168C(P)/8111C(P) Family PCI-E
Gigabit Ethernet NIC (NDIS 6.0)
Physical Address. . . . . . . . . : E0-CB-4E-AB-26-FA
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::51a8:4055:7e96:8789%10(Preferred)
IPv4 Address. . . . . . . . . . . : 10.116.160.2(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.116.160.1
DHCPv6 IAID . . . . . . . . . . . : 182504270
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-13-BD-A0-68-E0-CB-4E-AB-26-FA

DNS Servers . . . . . . . . . . . : ::1
10.116.160.2
NetBIOS over Tcpip. . . . . . . . : Enabled


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## grutz (Jun 5, 2008)

*Re: Changing Subnet Mask*

Client IPconfig /all

Microsoft Windows [Version 6.1.7600]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.

C:\Users\User>ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . : User-VAIO
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : levin.school

Wireless LAN adapter Wireless Network Connection:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . : levin.school
Description . . . . . . . . . . . : Intel(R) Centrino(R) Advanced-N 6200 AGN
Physical Address. . . . . . . . . : 00-23-14-48-A3-1C
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . : levin.school
Description . . . . . . . . . . . : Marvell Yukon 88E8059 PCI-E Gigabit Ether
net Controller
Physical Address. . . . . . . . . : 54-42-49-13-BB-E7
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::f8f4:86aa:bde0:efe5%11(Preferred)
IPv4 Address. . . . . . . . . . . : 10.116.160.50(Preferred)
Subnet Mask . . . . . . . . . . . : 255.0.0.0
Lease Obtained. . . . . . . . . . : Wednesday, 8 September 2010 3:07:35 p.m.
Lease Expires . . . . . . . . . . : Thursday, 16 September 2010 5:13:51 p.m.
Default Gateway . . . . . . . . . : 10.116.160.1
DHCP Server . . . . . . . . . . . : 10.116.160.2
DHCPv6 IAID . . . . . . . . . . . : 385885374
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-13-F6-32-FF-54-42-49-13-BB-E7

DNS Servers . . . . . . . . . . . : 10.116.160.2
Primary WINS Server . . . . . . . : 10.116.160.2
NetBIOS over Tcpip. . . . . . . . : Enabled


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## grutz (Jun 5, 2008)

*Re: Changing Subnet Mask*

To answer your question -Samurai

The server is not currently on the school network but at home and on DHCP is giving out the ip addresses but the subnet is incorrect. I have been unable to find anywhere in the DHCP or DNS where the subnet is recordered. If I remember correctly the IP and subnet was entered when I first installed the server software, before DHCP was configured.


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## 2xg (Aug 5, 2009)

*Re: Changing Subnet Mask*



> I'd love to change the subnet in DHCP console but cannot find it.


Open up Server Manager=> Roles=> DHCP Server=> in here you may change, delete or create a New Scope of IP Addresses and make sure that you type in the correct Subnet Mask also.


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## ThePistonDoctor (Mar 2, 2009)

*Re: Changing Subnet Mask*

If your SERVER is getting its DHCP info from another server, you need to physically (or remotely, really) go to that server and change the DHCP scope on the DHCP server. Remember, even though your new server is a "server," if it's getting a DHCP number it's still a client to another DHCP server. You need to change the mask on that one, or configure your server w/ a static IP and subnet mask.


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## grutz (Jun 5, 2008)

*Re: Changing Subnet Mask*

Thanks guys for the replies. I got it working by deleting the scope and creating another and making sure I changed the subnet mask to 255.255.255.0. 

Your suggestion 2xg looks similar but didn't need to use it.

And ThePistonDoctor - it's a primary school and only one server.

thanks


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