It appears from the IPs listed that you are using external Usermapper. The auto-broadcast feature is only needed for internal Usermapper, which runs on the Data Mover. Usermapper auto broadcast simply lets the other Data Movers know which Data Mover is running Usermapper. It would be broadcasting its internal IP address to the other Data Movers.

Here's an example of internal Usermapper running on server_2:

[nasadmin@cs0 nasadmin]$ server_cifs server_2
server_2 :
256 Cifs threads started
Security mode = NT
Max protocol = NT1
I18N mode = UNICODE
Home Directory Shares ENABLED, map=/.etc/homedir
Usermapper auto broadcast enabled
 
Usermapper[0] = [127.0.0.1] state:active (auto discovered)

Now, here's an example of server_3 seeing server_2's internal Usermapper:

[nasadmin@cs0 nasadmin]$ server_cifs server_3
server_3 :
256 Cifs threads started
Security mode = NT
Max protocol = NT1
I18N mode = UNICODE
Home Directory Shares ENABLED, map=/.etc/homedir
Usermapper auto broadcast enabled
 
Usermapper[0] = [192.168.1.2] state:active (auto discovered)
Usermapper[1] = [192.168.2.2] state:active (auto discovered)

Notice that the other Data Movers simply listen for the Data Mover running Usermapper and they use that IP address, no additional configuration needed.

hth