Recently while installing 11gr2 RAC I faced this issue. At after specifying VIP’s in CRS install I got INS-40910
From Oracle Database Error Messages
INS-40910: enter the virtual IP: string is invalid.
Cause: The virtual IP cannot resolve the IP address.
Action: IP address can be resolved to a valid Please enter a VIP.
Error looked to be very simple. i.e. VIP is not correct. But when I checked the /etc/hosts entries were correct
So I checked the installation log to see, what names are being used. CRS was trying to use, VIP address as node1-vip.xyz.com.
I did nslookup 10.182.187.106 & result was node1-vip. So entries in DNS were corrected & install was successful. So check if expected VIP is correctly resgitered in DNS (use nslookup to verify).