MSDP client deduplication fails
NetBackup client-side agents (including client deduplication) depend on reverse host name look up of NetBackup server names. Conversely, regular backups depend on forward host name resolution. Therefore, the backup of a client that deduplicates it's own data may fail, while a normal backup of the client may succeed.
If a client-side deduplication backup fails, verify that your Domain Name Server includes all permutations of the storage server name.
Also, Veritas recommends that you use fully-qualified domain names for your NetBackup environment.