DNS error when try to trace the server

Hi All,I am facing some problem in server to server connectivity. “ServerA” is not able to connect to “ServerB” unless i put IP address in Port tab in “ServerB” Server Document. When i try to Ping the “ServerB” server using common name or by FQDN from os level, i can able to ping the server means DNS entry is correct. But when i try to trace the “ServerB” it returns error as “DNS did not return an IP address for ServerB” Can someone pls help me.

Subject: Server Connection

Create a Server connection document or, if exists, make sure you have the IP address listed in the optional network address field.