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Multiple IPs and Outbound IP on 2008, best practice suggestion...

    Question

  • Hello,
    I need a suggestion on an issue;

    I have a Windows 2008 R2 SP1 Std. Ed. I have 3 IPs for that server, each of them uses the same gateway. By design the IP which is closest to the gateway is the default outbound IP on W2K8_R2_SP1_SE.

    I want to choose any other IP out of other 2 assigned IPs as default outbound one.

    example:

    GATEWAY: 10.0.0.1

    IP1: 10.0.0.2 (default outbound by design)

    IP2: 10.0.0.3 (the one I want it to be default outbound)

    IP3: 10.0.0.4 (not important)

    There are basically 2 choices available to me doable right now. Can you please take a moment and suggest one of the solutions below or state if you know the best practice for such a case? Thank you very much in advance =)

    First Solution:

    apply this command: Netsh int ipv4 add address 12 10.0.0.1 255.x.x.x skipassource=true

    then apply these 3 hotfixes:

    IP addresses are still registered on the DNS servers even if the IP addresses are not used for outgoing traffic on a computer that is running Windows 7 or Windows Server 2008 R2
    http://support.microsoft.com/kb/2386184
     
    The "skipassource" flag of IP addresses is cleared after you use the GUI to change IP settings of a network adapter in Windows 7 or in Windows Server 2008 R2
    http://support.microsoft.com/kb/2554859
     
    FIX: IIS Manager does not display IP addresses that are assigned to the network adapter together with the skipassource flag
    http://support.microsoft.com/kb/2551090

    Second Solution:

    Simply create 2 interfaces. Use the first one with the IP that I want to be as outbound default, dump all other IPs to the second interface. 2 interfaces will have the same gateway but Windows will assume the first one as the outbound default.

    Wednesday, March 05, 2014 2:01 PM

All replies

  • I believe you want to set the metric on the interfaces.

    You can do this by altering your routing table with route.exe or alternatively, you can change the interface metric in the TCP/IP advanced properties for your network adapter (via Control Panel). By default it uses an automatic metric (i.e. Windows chooses which interface to use).

    For your reference (and the reference of anyone else facing a similar challenge), the metric is a weighted value Windows will use to determine which interface to use for a particular endpoint. Here is the definition from the route.exe documentation:

    metric   Metric   Specifies an integer cost metric (ranging from 1 to 9999) for the route, which is used when choosing among multiple routes in the routing table that most closely match the destination address of a packet being forwarded. The route with the lowest metric is chosen. The metric can reflect the number of hops, the speed of the path, path reliability, path throughput, or administrative properties.


    Wednesday, March 05, 2014 2:37 PM
  • Thank you for answering. Unfortunately those are the only 2 options I have. Besides the first solution does not even include creating a second interface. So 'metrics' are irrelevant to my situation.

    Maybe I should not have said "best practice" but "better practice of the given two".

    Thank you...

    Wednesday, March 05, 2014 3:03 PM