Applies To:

Oracle version(s):11.2.x.x

Operating System(s):RHEL5.x, OEL5.x


Ramamohan Reddy


How to setup cluster nodes using GNS while installing Oracle RAC 11g R2?


To set up an Oracle 11g R2 RAC installation using Oracle Grid Naming Services (GNS) the following requirements need to be met:

  • At least two interfaces configured on each node, one for the private IP address and one for the public IP address.
  • A Domain Naming Server (DNS) running in the network for the address resolution of the GNS virtual IP address and hostname.
  • The DNS entry to configure the GNS sub-domain delegation
  • A DHCP server running on the same public network as your Oracle RAC cluster.


Table 1 describes the different interfaces, IP address settings, and the resolutions in a cluster.


Table 1. Interface Requirements









Not required

Node Virtual IP



GNS virtual IP



SCAN virtual IP




Configuring the DNS Server to support GNS

 To configure changes on a DNS server for an Oracle 11g R2 cluster using GNS:


  1. Configure GNS VIP address on DNS server—In the DNS, create a name resolution entry for the GNS virtual IP address in the forward lookup file.

For example: gns-server IN A

where gns-server is the GNS virtual IP address given during Oracle Grid installation. The address that you provide must be routable and should be in public IP address range.

  1. Configure the GNS sub-domain delegation—In the DNS, create an entry to establish a DNS lookup that directs the DNS resolution of a GNS subdomain to the cluster.

Add the following to the DNS lookup file: NS,

where is the GNS sub domain (provided during the Oracle Grid installation) that you delegate and resolves to the GNS virtual IP address.


Configuring a DNS Client

To configure the changes required on the cluster nodes for name resolution:

  1. You must configure the resolv.conf on the nodes in the cluster to contain name server entries that are resolvable to DNS server.

For example, edit the /etc/resolv.conf file as:

options attempts: 2

options timeout: 1





NOTE The total time-out period which is a combination of options attempted and options timed out should be less than 30 seconds. In the example above, is the valid DNS server address and is the GNS Virtual IP address in your network, and is the domain server in your network

  1. Verify the order configuration. /etc/nsswitch.conf controls the name service order. In some configurations, the NIS can cause issues with Oracle SCAN address resolution. It is recommended that you place the NIS entry at the end of the search list.

For example, hosts: dns files nis


Once the appropriate changes have been made run the following command to restart the service:

/sbin/service nscd restart

 Once done with configuring the DNS server client, during the Oracle Grid  installation provide the necessary information in the Oracle Universal Interface (OUI) to proceed with the installation.