Below are the steps for changing private interconnect details in oracle GRID/RAC  12c.

In our case we will change the private interface name from eth7 to eth8(after confirmation from network team).

1. Check the interface details : ( from root user)

[root@dbhost1 ~]$ $GRID_HOME/bin/oifcfg getif
bond0  global  public
eth7  global  cluster_interconnect,asm.  --- > This is the private interface

2. Now add the interface name: ( Do it from only one node)

In our case, we are only changing the interface name to eth8, So we have kept the ip same. If your network team is providing new private ip , then you update the ip accordingly.

[root@dbhost1 bin]# ./oifcfg setif -global eth8/,asm

3. Check the getif output:

[root@dbhost1 bin]# ./oifcfg getif
bond0  global  public
eth7  global  cluster_interconnect,asm
eth8  global  cluster_interconnect,asm
[root@dbhost1 bin]#

4. Disable and stop the crs( on both nodes)

[root@dbhost1 bin]#./crsctl stop crs
[root@dbhost1 bin]#./crsctl disable crs

5.Now request network Team to change the interface name:

Make sure ifconfig command is showing the new interface details also.

$ ifconfig -a

6. Start and enable the crs:[ Do on both the nodes]

[root@dbhost1 bin]#./crsctl start crs
[root@dbhost1 bin]#./crsctl enable crs

Ensure both the clusters are up and running fine.

7. Delete the old interface:

[root@dbhost1 bin]# ./oifcfg delif -global eth7/

[root@dbhost1 bin]# ./oifcfg getif
bond0  global  public
eth8  global  cluster_interconnect,asm