6 Replies Latest reply: May 20, 2013 12:11 PM by rarain RSS

    Why public and virtual IP in the same subnet

    1001135
      Hello every DBA,
      All in the title.
      Can someone tell me what is wrong if we separate "virtual IP" from "hostname" ?

      Thanks in advance
        • 1. Re: Why public and virtual IP in the same subnet
          rarain
          Hi,

          What exactly you want to know...In subject you asked "Why public and virtual IP in the same subnet" and in your question box you are asking "Can someone tell me what is wrong if we separate "virtual IP" from "hostname" ?".

          Public IP is assigned to Physical NIC which is meant for application to make the connection with Cluster nodes but if node is not running in that case application has to wait for network timeout before to attempt another address for connection but if application is using Virtual IP which actually doesn't exist physically but it is mapped on existing physical NIC (i.e. same NIC which we are using for Public network) in that case application immediately receive an error packet which enforce the application to use another connection address from the address list.

          Hope this information is useful for you. Let me know your question is something different what I have answered.

          Thanks
          • 2. Re: Why public and virtual IP in the same subnet
            1001135
            Thank you, but it doesn't answer to my question.
            I wasn't clear.
            So, here is my question : ( I hope more clearly)

            Oracle said that node1(=hostname) and node1-vip MUST be configured on the same subnet without explaining why.
            So, I tried ad try hard to understand why.
            I try to imagine If we configure node1-vip on EN1 when our node1 ( =hostname ) is on EN0, what kind of problem or example of problem can we meet ?

            Thanks in advance.
            • 3. Re: Why public and virtual IP in the same subnet
              Levi Pereira
              998132 wrote:
              Thank you, but it doesn't answer to my question.
              I wasn't clear.
              So, here is my question : ( I hope more clearly)

              Oracle said that node1(=hostname) and node1-vip MUST be configured on the same subnet without explaining why.
              So, I tried ad try hard to understand why.
              I try to imagine If we configure node1-vip on EN1 when our node1 ( =hostname ) is on EN0, what kind of problem or example of problem can we meet ?

              Can someone tell me what is wrong if we separate "virtual IP" from "hostname" ?
              Nothing. Is supported do that. The requeriment is VIP and SCAN be configured under a PUBLIC NETWORK, does not matter what public network you will use (you decide what you will use).


              All VIP/SCAN IP work as alias IP under Public Interface.
              These alias must be configure under existing network because the alias take configuration (such as gateway/subnet) of that network.

              This is the reason that you must use existing public network to create VIP and SCAN IP.

              Note:Also you can configure mutliple network (public) in a Oracle RAC, but VIP or SCAN always will be setup under it's own public network. That mean for each public network you will setup VIP or SCAN. (SCAN is supported in only one Public network, VIP is supported in multiple network)

              See this example:
              http://levipereira.wordpress.com/2011/10/22/how-configure-multiples-public-network-an-grid-infrastructure-11g-r2-11-2-environment/


              Regards,
              Levi Pereira

              Edited by: Levi Pereira on May 17, 2013 7:04 PM
              • 4. Re: Why public and virtual IP in the same subnet
                1001135
                Hi Levi,
                You said "The requeriment is VIP and SCAN be configured under a PUBLIC NETWORK"
                1) What does "PUBLIC NETWOK" mean ?
                2) Is that supported that "Scan Vip" and "primary vips" (= hostname-vip) could be on another network card than (hostname) ?
                I mean, is supported to have this example of configuratipon :
                eth0 : hostname
                eth1 : vips and scan vips
                eth2 : another application vips
                eth4 : private network

                Best regards.
                • 5. Re: Why public and virtual IP in the same subnet
                  Levi Pereira
                  998132 wrote:
                  Hi Levi,
                  You said "The requeriment is VIP and SCAN be configured under a PUBLIC NETWORK"
                  1) What does "PUBLIC NETWOK" mean ?
                  2) Is that supported that "Scan Vip" and "primary vips" (= hostname-vip) could be on another network card than (hostname) ?
                  I mean, is supported to have this example of configuratipon :
                  eth0 : hostname
                  eth1 : vips and scan vips
                  eth2 : another application vips
                  eth4 : private network
                  No. VIP or SCAN does not have fixed IP in a network interface they are dynamic, If a node fail they will move to available nodes of cluster. You don't need a interface to each VIP/SCAN and its does not make sense because they are not fixed IP.
                  e.g In a clusterware with 3 nodes and 2 nodes die, you will see in a public network all VIP and SCAN IP in one Node.

                  In others words VIP and SCAN are alias IP.
                  What is a IP Alias?
                  IP aliasing is associating more than one IP address to a network interface.
                  • 6. Re: Why public and virtual IP in the same subnet
                    rarain
                    Hi,

                    You have seen that while cluster installation it ask you to choose Public Interface card and Private Interface type for clusterware, let's say you selected eth0 as public interface and eth1 as private interface and these information also maintained in OCR disk. Now SCAN-VIP and NODE-VIP are just IP alias which can be only associated with public interface so there is no way to specify another interface for SCAN-VIP and NODE-VIP.

                    Thanks