The purpose of this post is to describe common questions on change or update of the private network (cluster_interconnect) information in Oracle Clusterware.
It may be necessary to change or update interface names, or subnet associated with an interface if there is a network change affecting the servers, or if the original information that was input during the installation was incorrect. It may also be the case that for some reason, the Oracle Interface Configuration Assistant (‘oifcfg’) did not succeed during the installation.
Network information(interface, subnet and role of each interface) for Oracle Clusterware is managed by ‘oifcfg’, but actual IP address for each interfaces are not, ‘oifcfg’ can not update IP address information. ‘oifcfg getif’ can be used to find out currently configured interfaces in OCR:
% $CRS_HOME/bin/oifcfg getif [interfacename]0 10.X.XXX.0 global public [interfacename]1 192.XXX.X.0 global cluster_interconnect
On Unix/Linux systems, the interface names are generally assigned by the OS, and standard names vary by platform. For Windows systems, see additional notes below. Above example shows currently interface [interfacename]0 is used for public with subnet 10.2.156.0, and [interfacename]1 for cluster_interconnect/private with subnet 192.168.0.0.
The ‘public’ network is for database client communication (VIP also uses the same network though it’s stored in OCR as separate entry), whereas the ‘cluster_interconnect’ network is for RDBMS/ASM cache fusion. Starting with 11gR2, cluster_interconnect is also used for clusterware heartbeats – this is a significant change compared to prior release as pre-11gR2 uses the private nodename that were specified at installation time for clusterware heartbeats.
If the subnet or interface name for ‘cluster_interconnect’ interface is incorrect, it needs to be changed as crs/grid user.
Changing private hostname
In pre-11.2 Oracle Clusterware, private hostname is recorded in OCR, it can not be updated. Generally private hostname is not required to change. Its associated IP can be changed. The only way to change private hostname is by deleting/adding nodes, or reinstall Oracle Clusterware.
In 11.2 Grid Infrastructure, private hostname is no longer recorded in OCR and there is no dependency on the private hostname. It can be changed freely in /etc/hosts.
Changing private IP only without changing network interface, subnet and netmask or changing private IP MAC address only without changing anything else
For example, private IP is changed from 192.XXX.X.10 to 192.XXX.X.21, network interface name and subnet remain the same, or MAC address is changed, private IP address/interface name/subnet/network all remain the same.
Simply shutdown Oracle Clusterware stack on the node where change required, make IP or MAC modification at OS layer as required (eg: /etc/hosts, OS network config etc) for private network, restart Oracle Clusterware stack will complete the task.
Changing private network MTU only
For example, private network MTU is changed from 1500 to 9000 (enable jumbo frame), network interface name and subnet remain the same.
1. Shutdown Oracle Clusterware stack on all nodes.
2. Make the required network change of MTU size at OS network layer, ensure private network is available with the desired MTU size, ping with the desired MTU size works on all cluster nodes.
3. Restart Oracle Clusterware stack on all nodes.