Replication Server version 15.7.1 - Sybase ASE 15.5, how to change primary data server in RSSD?

Recently, I am requested to migrate the current Sybase data server to a new Sybase data server (let's say, from pub1 to pub2). To do this, I need to rebuild all the RepAgents which have been set up previously in pub1. Is there any primary data server I would need to set in the RSSD? Because I could see when I run the command 'connect' without any option, it will connect to (pub1.repserver) instead of (pub2.repserver). Is there any configuration required on the RSSD to make it (pub2.repserver)? Also, I actually have setup one RepAgent (pub2.db_lotte), the setup process using rs_init was successful, but seems the RepAgent connection is down after the setup process (admin who_is_down), the connection couldn't bring up and no error is captured in the replication log. Appreciate if anyone could help. Thanks.