PRVG-01172: The IP address "{0}" is on multiple interfaces "{1}" on nodes "{2}"

Hi,
Any network guru's out there? We are upgrading a 12.2.3 EBS database 11.2.0.4 to 12.1.0.2 . It is 2 rac nodes, 2 apps tiers.

We have this error when running runcluvfy.sh for preinstall checks for the cluster.   The same ip is setup on both nodes of the rac cluster.

PRVG-01172: The IP address "{0}" is on multiple interfaces "{1}" on nodes "{2}"

Cause: The given IP address was found on multiple interfaces, when an IP address can be on at most one interface.

Action: Remove the given IP address from all but one interface on each node.

A few questions

1.  How to remove the double IP?

2. What is the command to setup the eth0 's? Is this something a network engineer would know or something that is in the docs to setup RAC?