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Configuring Virtual IP for RAC

Oracle RAC Cluster Tips by Burleson Consulting

In order to install or upgrade to Oracle Database 10g RAC, the use of a virtual IP address to mask the individual IPO addresses of the clustered nodes is required. The virtual IP addresses are used to simplify failover and are automatically managed by CRS.

To create a Virtual IP (VIP) address, the Virtual IP Configuration Assistant (VIPCA) is called from the script of a RAC install, which then configures the virtual IP addresses for each node specified during the installation process. In order to be able to run VIPCA, there must be unused public IP addresses available for each node that has been configured in the /etc/hosts file.

This means that when installing 10g RAC, at least three network interfaces are required for each node in the RAC cluster, these are:

* Public Interface:  Used for normal network communications to the node

* Virtual (Public) Interface: Used for failover and RAC management

* Private Interface:  Used as the cluster interconnect

The Oracle 10g RAC installation guide states the following requirements for installing RAC:

* External shared disks. 

* One private internet protocol (IP) address for each node to serve as the private cluster interconnect. This IP address must be separate from the public network, and it must have the same interface name on every node that is part of the cluster.  This requires its own high speed network interface card (NIC).

* One public IP address for each node to use for its Virtual IP address for client connections and for connection failover. This IP address is in addition to the operating system managed public host IP address that is already assigned to the node by the operating system. This public Virtual IP must be associated with the same interface name on every node that is a part of the cluster. The IP addresses that are used for all of the nodes that are part of a cluster must be from the same subnet. The host names for the VIP addresses must be registered with the domain name server (DNS). The Virtual IP address should not be in use at the time of the installation because this is a Virtual IP address that Oracle manages internally to the RAC processes. This virtual IP address does not require a separate NIC.

* Redundant switches as a standard configuration for all cluster sizes; however, they will not be checked for. 

In order to verify that each node meets the network requirements, you should follow these steps:

1. Verify the presence of or install a minimum of two NICs for the public and private networks and configure them with either public or private IP addresses.

2. Use OS utilities to register the host names and IP addresses for the public network interfaces in DNS.

3. For each node in the cluster, register the virtual host name and IP address in DNS.

4. Edit the /etc/hosts file on UNIX or Linux, and add the private, public, and virtual interfaces.  

The following is an example on a two-node Linux system:

            [aultlinux1]/etc> more /etc/hosts
            # Do not remove the following line, or various programs
            # that require network functionality will fail.
         aultlinux1 localhost.localdomain   localhost

In this example, the int-* addresses are private and the *-v addresses are for the virtual IP's.

To identify the interface name and associated IP address for every network adapter, the following command can be entered: 

             # /sbin/ifconfig -a
            ...or /usr/bin/netstat -in on HP-UX
    ...or ipconfig on Windows

The virtual IP's do not have to be added to IFCONFIG.  This is because the VIPCA takes care of it.

At this point, if everything is properly configured, it should be possible to ping the public IP names from any of the machines on the network.  For example:

[aultlinux2]/home/oracle>ping aultlinux1
            Pinging [] with 32 bytes
            Reply from bytes=32 time<10ms TTL=255
            Reply from bytes=32 time<10ms TTL=255

At this point, it should also be possible to do an NSLOOKUP on the virtual IP names:

[aultlinux2]/home/oracle>nslookup aultlinux1-v


This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters, Rampant TechPress, by Mike Ault and Madhu Tumma.

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.


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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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