DHCP unable to issue IP address on workstation with different VLAN ?

People,

I've migrated the DHCP server role from one old Win2k3 server (IP: 10.1.1.2) to the new Win2k12R2 (IP: 10.1.1.106) server which still in the same IP Subnet / VLAN.

Server VLAN: 10.1.1.0/24
Workstation VLAN: 10.1.2.0/24, 10.1.3.0/24, ... until 10.1.8.0/24

However after the role migration, the DHCP is not working for the wired network, but it work with the Wireless LAN which assign the IP address class/VLAN 10.1.1.0/24 asme with the server subnet.

My laptop Ethernet conenction is in 10.1.8.0/24 range and it doesn't work at all.

what could be the culprit in this cause ?

Any help or comment pointer in this case would be greatly appreciated.

THanks,
LVL 9
Senior IT System EngineerIT ProfessionalAsked:
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Will SzymkowskiSenior Solution ArchitectCommented:
You are 100% correct. If your DHCP server is sitting on 10.1.1.1.x and your workstations are on 10.1.2.x and so on... then you HAVE to add the IP Helper address to your switches that are on the 10.1.2.x... vlan.

You need to do this because DHCP brodcast will not go across vlans naively you need to tell the clients where to go for DHCP broadcast, which is on another vlan.

If you have a server that has a dhcp set it will work no problem, but the workstations are another story. This is DHCP 101 when working with multiple vlans.

You will need to add the helper address to all of your switches that hold the workstation vlan.

Will.
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Senior IT System EngineerIT ProfessionalAuthor Commented:
Which Event ID should I need to look in the server or the workstation client (Win7 and Win 8.1) ?

Does this issue can be caused by DHCP helper on the switch or router ?
if so how to proof it is that's the case ?
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Senior IT System EngineerIT ProfessionalAuthor Commented:
ok, so what is the error message on the DHCP server or the workstation if this is the case ?
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Will SzymkowskiSenior Solution ArchitectCommented:
You tell me. I do not have this setup so I cannot tell you exactly what error messages you are going to see on the workstations.

All you need to do is filter the System/application. Log for warnings/errors.

That being said if you know that you have not assigned an IP helper then why do you need to reference a event log? If there is no IP helper in place users on a different VLAN from the DHCP server will not get a DHCP address period.

Will.
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it_saigeDeveloperCommented:
Was it working before?  Will is spot on, you have to change the IP Helper address on the VLAN configuration so that it contains the new server IP address.

-saige-
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Senior IT System EngineerIT ProfessionalAuthor Commented:
yes, before I migrated the DHCP role to the new server with different IP address within the same subnet.
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Will SzymkowskiSenior Solution ArchitectCommented:
Whatever IP address you have changed your DHCP server to you need to add this one to the IP helper on the vlan configuration. I would also remove the old IP as well.

There is nothing else to explain, that's all you need to do.

Will.
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Senior IT System EngineerIT ProfessionalAuthor Commented:
Thanks !
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Senior IT System EngineerIT ProfessionalAuthor Commented:
You are right Will, as I thought before there is a DHCP helper in the switch.

But in this case, the Network engineer suggest me to switch the IP address of the old Win2k3 DC with the new Win2k12 DC IP adddress and vice versa.

At the moment which only works with the old domain controller:
10.1.1.13 - Old DC/GC 2003 (DNS & DHCP)
10.1.1.199 - New DC/GC 2012 R2 (DNS & DHCP)

Suggested changes:
10.1.1.199 - Old DC/GC 2003 (DNS & DHCP)
10.1.1.13 - New DC/GC 2012 R2 (DNS & DHCP)

is there any problem with changing or swapping the IP address of a domain controller which is also running as GC & DNS server ?
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it_saigeDeveloperCommented:
Should not be any problems.

-saige-
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