Please make use of below steps for connection related issues in sql server
Step1:
First check below ping information related to the specific server.
C:\Documents and Settings\username>ping servername
Pinging servername.xx.yyy.com [12.345.67.890] with 32 bytes of data:
Reply from 12.345.67.890: bytes=32 time=96ms TTL=122
Reply from 12.345.67.890: bytes=32 time=95ms TTL=122
Reply from 12.345.67.890: bytes=32 time=95ms TTL=122
Reply from 12.345.67.890: bytes=32 time=96ms TTL=122
Ping statistics for 12.345.67.890:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 95ms, Maximum = 96ms, Average = 95ms
--------------------------------------------------------------------------------
C:\Documents and Settings\ username >ping -a 12.345.67.890
Pinging servername [12.345.67.890] with 32 bytes of data:
Reply from 12.345.67.890: bytes=32 time=97ms TTL=122
Reply from 12.345.67.890: bytes=32 time=95ms TTL=122
Reply from 12.345.67.890: bytes=32 time=95ms TTL=122
Reply from 12.345.67.890: bytes=32 time=95ms TTL=122
Ping statistics for 12.345.67.890:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 95ms, Maximum = 97ms, Average = 95ms
---------------------------------------------------------------------------------
If I ping server name, it show server name with fully qualified name. If I reverse ping with ip address, it show only server name not with fully qualified name.
We couldn't able to find fully qualified name along with server name.
Step2:
Resolution:
Ask DNS support team to make changes in DNS entry to resolve above reverse ping issue.
After that change, we can able to connect SQL server with no issues.