Resolution:
When EMS failover occurs or EMS is restarted, in tibemsadmin some FT connections may show "unknown" under "Host"  and "<unable to get address information>" under "IP address". The EMS serverdoes not store host/IP information for FT connections in meta.db. Before these connections reconnect back after failover or restarting of EMS, "Host" and "IP address" of these information will not be shown in tibemsadmin.  After these connections are reconnected, "Host" and "IP address" information will be displayed. If these connections are not reconnected before ft_reconnect_timeout (in tibemsd.conf) is reached, the EMS server will purge the connections. The following message can be shown in the server log:

[anonymous@<unable to get address information>]: connection id=xxx purged after FT timeout 

Note that if max_connections (in tibemsd.conf) is non-zero, these connections are counted in max_connections.

Why do FT connections show "unknown" host in tibemsadmin.