There's a lot of confusion (by customers AND TSEs!) about what's supported where RedHat is concerned. Too often focus lands squarely on the kernel version...when our Compatibility Matrix doesn't mention kernel versions AT ALL!
To get a better handle on whether or not you're supported and if so, what you need to install, let's get output from these commands from you:
# uname -a
# cat /etc/redhat-release
Then we'll know EXACTLY which version of RedHat you've got as well as on which architecture you're running it. After that, it should be a piece of cake to look you up using the matrix:
Veritas NetBackup (tm) 6.x Operating System Compatibility List (Updated April 22, 2009)
http://support.veritas.com/docs/278064