Oracle 11.2.0.3 upgrade precheck error: "PRVF-4190 : Verification of the hosts config file failed"

When I was upgrading Oracle 11.2.0.1 RAC database to 11.2.0.3 on Linux RHEL5 environment the prerequisite checks gaved following error:
"PRVF-4190 : Verification of the hosts config file failed"

This means that there is something wrong in the /etc/hosts file. Following MOS (My Oracle Support) ID gives more info about this:

[ID 1056025.1]

But in this time I was using same /etc/hosts file in several other RAC installations both 11.2.0.1 and 11.2.0.3 . And all of those were working nicely and none of those gaved this error when installing them. So it seems that upgrade is doing this check some other way than pure install of 11.2.0.3. (In my case this fail is probably because there is a lot of IPv6 addresses in hosts file. Thought that hosts file is still valid and working fine.)

I made SR about this and response was that I can ignore error because same file is working fine with other databases. So I ignored it and run upgrade. Upgrade went ok but after root scripts cluvfy (Oracle Cluster Verification Utility) was failing because the same error about hosts file. I checked the installAction log file and there was no other errors than hosts file error. So I hit the skip button and then finished installation and everything is working just fine.

So the point here is that if upgrade precheck is failing because of the hosts file (PRVF-4190) it can be ignored if it is not failing with clean installations and the hosts file is valid+working fine elsewhere.