Ping all hostnames (Public, Private) from each host and see if all ping commands work and return correct IP addresses.
On both name, run 'hostname" command to double check the host names of both and make sure they are same as in host file.
Before attempting the GI install, did you get a clean run of the Cluster Verification Utility? The CVU is able to spot these things in advance.
As suggested by "Brian" it is highly recommend to run Cluster Verification utility before starting Installer for GI.
X A H E E R