NetBackup Auto Image Replication configuration fails, "Error in fetching storage server information configured with : cannot connect on socket(25)"

Problem

NetBackup (NB) Auto Image Replication (AIR) configuration, specifically while in the NB java-based administration console Media and Device Management > Credentials > Storage Servers > properties of the storage server Replication tab in Add a Replication Target in a Different NetBackup Domain to add the target master the following error occurs:

Error Message

"Error in fetching storage server information configured with <target_master>: cannot connect on socket(25)"

Cause

A network connectivity issue exists from source NB domain to target NB domain PBX TCP 1556 port.

Solution

Ensure the source and target NB domains can communicate with each other over the network, specifically open the TCP port for PBX/1556 between the master servers, and from the Source MSDP server to the target Master for the CA certificate.
 

Reference article:
NetBackup 6.x/7.x/8.x/9.x firewall port requirements
https://www.veritas.com/support/en_US/article.100002391