I think you need to use unique resolvable addresses. Netbackup is picky about forward/reverse DNS lookups.
In my cluster I have :
1IP for node1 {moon}.domain.com
1IP for node2 {gaia}.domain.com
1IP for the VCS service {clusterservice}.domain.com (that would be the HACAMP for you, I guess)
1IP for Netbackup {sky}.domain.com
Both host IP, VCS service IP, and Netbackup IP run through the same NIC. But all DNS names and their IP are unique.
Regards
Nicolai