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Windows Server 2008 R2 Thread, DHCP set to wrong ip in Technical; Hi, We have 1 server at a very small primary school that runs everything (DC, DNS DHCP). This server has ...
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    DHCP set to wrong ip

    Hi, We have 1 server at a very small primary school that runs everything (DC, DNS DHCP). This server has the ip X.X.X.1 on NIC1.

    When I type ipconfig /all on a client computer it lists DHCP as being on X.X.X.2

    X.X.X.2 on the server is NIC2 and assigned to hyper-v.

    If I disable NIC2 on the server and do a ipconfig renew on a client computer it comes back correct with X.X.X.1

    Why is this happening? I need NIC2 enabled for our Hyper-V.

    Is it something to do with the Hyper-v setting 'Allow management operating systems to share this network adapter' which I have ticked?
    Last edited by edutech4schools; 4th September 2012 at 11:21 AM.

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    ADMaster's Avatar
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    I’ve not used hyper V but can clients talk to your DC on x.x.x.2?
    If x.x.x.1 and x.x.x.2 are the same subnet and your clients are getting address from the correct range I wouldn’t worry too much.
    Should your hyper V nic be on a different subnet? Then your dhcp clients wouldn’t get an address from it.

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    The reason I started to investigate was due to computers falling of the network (not mapping drives etc) which cleared up after I disabled NIC2 on the server. This could have been coincidence so next week I will enable NIC2 and see what happens.

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    VeryPC_Ed's Avatar
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    I'm guessing from the above that DHCP is running on the host partition of the Hyper-V server ?

    Check in DHCP to see what I.P DHCP is binded to.

    Ideally if you have more than 1 nic, you should have a dedicated NIC with static I.P for management of the host and then route everything else from the VM's via a dedicated Virtual Network (non shared), personally I wouldn't run any services on the host partition (as your not supposed to anyway) but I wouldn't advise sharing the nic anyway if you can avoid it !

    Let me know if you need any help !
    Last edited by VeryPC_Ed; 5th September 2012 at 02:15 PM.

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    mac_shinobi (5th September 2012)

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    Thanks VeryPC_ed

    The server has 2 nics. I have assigned DHCP, DNS etc to run through NIC1. I then enabled NIC2, setup Hyper-v and only used NIC2 as the Hyper-v network. When I go to networks adapters NIC2 is now the virtual NIC and a new NIC has been created which has the standard settings that I had assigned to NIC2 (IP = x.x.x.2, DNS = x.x.x.1).

    This is the first time I have set up hyper-v. Is my setup not dedicating hyper-v to NIC2?

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    VeryPC_Ed's Avatar
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    If you have it setup with services on the host partition, I'd uncheck the 'allow management operating system to share this network adapter' option in virtual network manager, on the NIC dedicated for VM traffic, you shouldn't see any I.P details for it as the virtual switch will handle it all - so this way you will have all and any service traffic sent over the management nic and the VM traffic over the other.

    Ideally you should keep services off the host/parent partition (physical server) and run them inside the guests as a best practice, this way you minimise the chances of any knock on effects to the guest operating systems such as if you had to run a critical security update or a BSOD due to some application or service screwing up and taking everything else with it, not to mention performance.

    I believe there were some issues regarding appropriate licensing also for Server 2008 (not sure about R2 off the top of my head but I think it's the same), where if you were using the maximum licenses for the edition (see below) for the guests then you cannot run services in the host/parent partition.

    Standard - 1 Physical - 1 Virtual
    Enterprise - 1 Physical - 4 Virtual
    Datacenter - 1 Physical - Unlimited Virtual

    So if you were using Standard and had one VM, you shouldn't run apps/services on the host etc.

    If you need any more information, let me know !
    Last edited by VeryPC_Ed; 6th September 2012 at 11:35 AM. Reason: minor edit

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    edutech4schools (11th September 2012)

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    I unchecked the 'allow management operating to share' and all ok. Thanks.

    You are correct about the licencing which is why we have two standard licences.

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    VeryPC_Ed's Avatar
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    Glad to hear that's sorted out !

    If you have any Hyper-V questions in future, drop me a line and I'd be happy to help !

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