Multiple NICs in same segment server 2008

Discussion in 'Server Networking' started by dcohn, Jun 4, 2009.

  1. dcohn

    dcohn Guest

    I have anew Server 2008 server with multiple NICs. The Server is going to be
    running HYPER-V. I have a Management NIC and 2 more NICs that are bound to
    the same network segment and use Public IPs.

    The first NIC gets the gateway. The 2nd and thrid NIC I do not assign a
    Gateway. I set the order of the NICs so the one with the Gateway is at the
    top.

    When viewing in Route Print it says ON-LINK for the 2nd and thrid NIC.

    I can talk to these NICs locally from other servers on the same segment but
    nothing outside the network. If I add a route it works just fine. As you
    know if you attempt to assign a Gateway to a second NIC an error message is
    thrown telling you that you should not be assigning multiple Gateways.

    In the past I have never had routing issues on second or third NICs on the
    same segment. This seems to be specific to Server 2008.

    Firewall is disabled.
    \
    I am betting there is a simple solution but I have been unable to find it
    hence this post
     
    dcohn, Jun 4, 2009
    #1
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  2. dcohn

    dcohn Guest

    All of them use Public IPs.

    It is the same network and the same segment hence the reason the primary
    gateway should affect the second and third nics.

    I have the same config on a server 2003 and the additional NICs work fine.

    The IPCONFIG is huge as there are 8 NIcs and IPV6 as well (Not being used
    but left enabled)

    It is simply three NICs. Imagine the IPs below but they are PUBLIC IPS NOT
    natted IPs. All going to one GIG Switch in the same VLAN.

    I hope that is clear now. Nothing complicated here.

    NIC 1 is.

    10.1.1.10
    255.255.255.0
    10.1.1.1
    DNS
    10.1.1.5
    10.1.1.6

    NIC 2 is.

    10.1.1.11
    255.255.255.0
    No Gateway
    DNS
    10.1.1.5
    10.1.1.6

    NIC 3 is.

    10.1.1.12
    255.255.255.0
    No Gateway
    DNS
    10.1.1.5
    10.1.1.6
     
    dcohn, Jun 4, 2009
    #2
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  3. dcohn

    Bill Grant Guest


    Why do you have three NICs in the same IP subnet assigned to the
    machine? What purpose do they serve?

    If you are planning to use the second and third NICs for vms running
    under Hyper-V, the problem will go away. Once the NICs are assigned to a
    virtual switch for the vms to use, they do not require an IP address on the
    host.
     
    Bill Grant, Jun 4, 2009
    #3
  4. [snipped]

    Hello Dcohn,

    In addition to Bill's reply, if an interface doesn't have a gateway, and it
    receives a request on that specific NIC, it won't be able to respond if it
    doesn't have a gate if the NICs are on the same subnet. Why not just team
    them for balancing and fault tolerance? You can assign individual IPs on the
    VM guests independent of the host.

    --
    Ace

    This posting is provided "AS-IS" with no warranties or guarantees and
    confers no rights.

    Ace Fekay, MCSE 2003 & 2000, MCSA 2003 & 2000, MCSA Messaging, MCT
    Microsoft Certified Trainer


    For urgent issues, you may want to contact Microsoft PSS directly. Please
    check http://support.microsoft.com for regional support phone numbers.

    "Efficiency is doing things right; effectiveness is doing the right
    things." - Peter F. Drucker
    http://twitter.com/acefekay
     
    Ace Fekay [Microsoft Certified Trainer], Jun 4, 2009
    #4
  5. dcohn

    dcohn Guest

    That is correct HYPER V. But if you create a Virtual Switch the NIC must
    first have assigned IPs and gateways NO?????? QUESTION THAT IS ACTUALLY....
    Or is it simply based on the network address assigned to the VMs and where
    the NIC used for the VS is physically cabled?

    I thought I had to make the NICs working before assigning them to a switch.
    Wasn't that true of Virtual Server 2005?

    I cannot team them to use with HYPER-V to answer another post.

    What would be different if I select Private or public when creating the
    VSwitch as well.



    :

    Why do you have three NICs in the same IP subnet assigned to the
    machine? What purpose do they serve?

    If you are planning to use the second and third NICs for vms running
    under Hyper-V, the problem will go away. Once the NICs are assigned to a
    virtual switch for the vms to use, they do not require an IP address on the
    host.
     
    dcohn, Jun 8, 2009
    #5
  6. dcohn

    dcohn Guest

    CAN I TEAM NICS I AM USING for a Virtual Switch?? I thought this was a NO NO?


    You said

    Why not just team
    them for balancing and fault tolerance? You can assign individual IPs on the
    VM guests independent of the host.

    :
     
    dcohn, Jun 8, 2009
    #6

  7. I was speaking of the machine NICs itself. I had a server running with
    teamed NICs using Virtual Server without a problem. I just assigned the
    guests their own IP configs.

    Ace
     
    Ace Fekay [Microsoft Certified Trainer], Jun 9, 2009
    #7
  8. dcohn

    Bill Grant Guest

    There were problems with NIC teaming and Hyper-V early on. The
    manufacturers were slow to bring out drivers which were compatible with the
    Hyper-V networking software. The latest versions from Broadcom and Intel
    should handle NIC teaming, if you really need it.

    Networking in Hyper-V is very different from Virtual Server.
     
    Bill Grant, Jun 9, 2009
    #8
  9. I wasn't aware of the driver issues early on, but aware the two are
    different. Are you saying the later drivers, and possibly 2008 SP2 covers
    the issue?

    Ace
     
    Ace Fekay [Microsoft Certified Trainer], Jun 9, 2009
    #9
  10. dcohn

    Bill Grant Guest

    I don't run NIC teaming myself (although I do have multiple NICs in the
    host), but postings in the forums indicate that the latest NIC teaming
    software works fine with Hyper-V-enabled NICs. There were heaps of problems
    when Hyper-V was first released.

    Not sure about any improvements with SP2. There are certainly changes
    and improvements to networking in Hyper-V with R2!
     
    Bill Grant, Jun 9, 2009
    #10
  11. dcohn

    Bill Grant Guest


    When you create an external virtual switch in Hyper-V (ie one linked to
    a physical NIC) it does not work like installing VMNS in Virtual Server. See
    this article from Ben's blog.

    http://blogs.msdn.com/virtual_pc_guy/archive/2008/01/08/understanding-networking-with-hyper-v.aspx

    If you administer the server remotely, it is recommended to reserve one
    NIC in the host for this purpose (ie do not create a virtual network linked
    to this NIC) and use the other NIC(s) for vms. This is easier in R2 as they
    have made it more obvious in the GUI.
     
    Bill Grant, Jun 9, 2009
    #11
  12. Thanks, Bill!
     
    Ace Fekay [Microsoft Certified Trainer], Jun 9, 2009
    #12
  13. dcohn

    dcohn Guest

    Thanks

    I have a dedicated NIC just for management. I also have taken your advice
    that the NIC settings are irrelevant if I am creating a Virtual switch. But
    I did not see this before I setup and it is not 100% clear anyway as they
    seem to refer to just a single NIC. The issue was multiple NICs and whether
    they required any settings BEFORE Creating a VS.

    I NOW BELIEVE the best thing would have been to take bare unconfigured NICs
    and use them as the VS NICs as long as they are physically plugged into the
    correct segment for the access desired.

    Using your info I removed the gateways from the Virtual Nics (they took the
    settings I had applied to the physical NICs). Everything works fine without
    those gateways as you stated.

    It seems I Do NOT need to bind an IP address to the Virtual NICs? RIGHT?

    Since I already have created the VS can I just change those NIC settings to
    obtain automatically (we have NO DHCP Servers as this is a data center with
    only servers) and then I would not be wasting those IPs.

    Seems like a PLAN.

    I don't know why I assumed I needed the IP address but it is really not
    stated anywhere and habit caused me to do it. I follow now and it is quite
    clear.
     
    dcohn, Jun 9, 2009
    #13
  14. dcohn

    Bill Grant Guest

    No, the NIC does not need an IP address on the host. If you set the vms to
    get their network config automatically, they will get their config from the
    DHCP on the LAN.

    As far as the networking software is concerned, each vm connected through
    this NIC is just another machine on the LAN (the virtual switch works just
    like a physical switch plugged into this port) and the host machine is
    invisible through this NIC.

    To get this set up in Virtual Server, you had to clear all the boxes
    except VMNS in the TCP/IP settings on the host (to get a NIC dedicated to
    the guests only) or clear only VMNS (to get a NIC dedicated to the host).
     
    Bill Grant, Jun 10, 2009
    #14
  15. dcohn

    dcohn Guest

    Thanks very much.

    Just some minor confusion.

    I also checked my W2K3 server with muttiple NICs and the additional NICs are
    on private networks where they are used simply for access to local DATA ona
    Layer 2 switch. NO routing.

    The only other place I have multiple NICs I have them Teamed also.

    The real lesson learned is to use NICs with no configuration plugged into
    the segment desired as Virtual Switches. They just work and I have tons of
    bandwiidth on this box as well.

    THANKS

    Doug
     
    dcohn, Jun 10, 2009
    #15
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