About IP Address Requirements

When performing a typical installation of the Oracle Grid Infrastructure software, Grid Naming Service (GNS) is configured. Grid Naming Service uses multicast Domain Name Service (mDNS) to enable the cluster to assign hostnames and IP addresses dynamically as nodes are added and removed from the cluster, without requiring additional network address configuration in the domain name server (DNS).

When you use GNS, only one static IP address is required for the cluster, the GNS VIP address. All other node addresses can be obtained dynamically using DHCP. You define this address in the GNS domain during installation.This address must be configured in DNS. GNS manages the names of all virtual IP names for cluster nodes. You do not need to configure IP addresses for the individual nodes.

To enable GNS, you must have your network administrator provide DHCP with a set of IP addresses for the cluster and set up sub-domain forwarding to the GNS VIP (where the GNS will listen) in the coporate DNS. The DHCP must have enough IP addresses to support 3 SCAN VIPs for the cluster and 1 VIP for each node in the cluster. If you also use DHCP for the host IP then it must also have enough IPs for each Host in the cluster.

If chose not to perform a typical installation as shown in this guide, and you do not enable GNS, then you must configure the following addresses manually in your coporate DNS:

• A public IP address for each node

• A virtual IP address for each node

• Three single client access name (SCAN) addresses for the cluster

During installation a SCAN for the cluster is configured, which is a domain name that resolves to all the SCAN addresses allocated for the cluster. The IP addresses used for the SCAN addresses must be on the same subnet as the VIP addresses. The SCAN must be unique within your network. The SCAN addresses should not respond to ping commands before installation.

During installation of the Oracle Grid Infrastructure, a listener is created for each of the SCAN addresses. Clients that access the Oracle RAC database should use the SCAN or SCAN address, not the VIP name or address. If an application uses a SCAN to connect to the cluster database, the network configuration files on the client computer do not need to be modified when nodes are added to or removed from the cluster. The SCAN and its associated IP addresses provide a stable name for clients to use for connections, independent of the nodes that make up the cluster. Clients can connect to the cluster database using the easy connect naming method and the SCAN.