Help configuring Hyper V to see two different subnets

Posted on 2013-06-24
Medium Priority
Last Modified: 2016-11-24
My new Dell PE R270 sever has 4 NICs
We have two CISCO switches that use two VLANS.  

VLan10 ( for 169.2.71.x subnet) and VLan 100 (for 169.2.72.x subnet) whose ports are divided up between both switches.

The new Hyper V server will hold my DHCP server which serves up IPs to the 71 subnet for desktops as well as some scanning servers for the same subnet.

The other servers will be on the 72 subnet.

Will my host's NICs route the DHCP servers traffic or do i need to assign one of the NICs on the host a 71 address and then create a Hyper V virtual network and assign that NIC.  Then add the DHCP to that Virtual Network?

Or do i simply create a Hyper V Virtual Network as external and assign it any host NIC?

please advise
Question by:lgarza
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LVL 85

Expert Comment

by:David Johnson, CD, MVP
ID: 39272920
DHCP is initiated by the client by broadcasting to all and then await a response so just using an configuring the dhcp virtual machine to external network and bind it to a network adapter.

Author Comment

ID: 39272953
that is what I thought.  but, i get a 169.254.x.x ip on the newly created virtual.     never picks up an IP from my dhcp.
LVL 85

Expert Comment

by:David Johnson, CD, MVP
ID: 39273000
Have you told the DHCP virtual machine to use the proper VLAN?
You understand that a vlan is a method of having two networks use the same ip address range and be isolated from each other.
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Author Comment

ID: 39273031
No, I haven't.  Sorry, we have been on VM Ware, where I never needed to specify a VLAN ID.  So, "telling the DHCP virtual machine" is by typing in the VLAN ID when I configure the Hyper V virtual network?
LVL 85

Expert Comment

by:David Johnson, CD, MVP
ID: 39273038
you should probably set up a virtual network switch as well
LVL 20

Expert Comment

by:Svet Paperov
ID: 39273245
Configuring the network on Hyper-V is relatively easy task. However, I have to ask some questions:
- Why do you need DHCP on the Hyper-V host? First – DHCP is always a security risk, second – by adding an additional service to the host, you cannot use the free Windows Server licence for it (for example when you install Windows Server 2012 as a host, you are able to install 2 virtual machines, but you can't use your host for any other purpose but for virtualization)
- Do you need VLAN trunking over a single NIC or you will plug each NIC in its own IP subnet (no need of VLAN)?

The best design, in my opinion, will be:
- Put the host server in its own segment and in its own domain (or leave it as Workgroup): keep NIC 1 only for the management traffic to the host
- Set one of the virtual servers as DHCP and attach a virtual NIC in 169.2.71.x subnet: NIC 2
- Use NIC 3 to create a virtual NIC (virtual switch) for 169.2.72.x subnet and use it to the other servers (optionally, you can team NIC 3 and 4 and then create a virtual NIC to better performance)
- Disable “Allow management operating system to share this network adapter” on both virtual NICs
- You will need a router to route between both subnets and, eventually, the management one
No VLAN IDs are used in this scenario

Accepted Solution

lgarza earned 0 total points
ID: 39285350
Solution:  Was to simply change the switch port i'm attached to from an access port to a trunk port.

I can now access both VLANs

Author Closing Comment

ID: 39296012
this was  a self resolved issue.    i changed the cisco switch port to be a trunk port.

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