Sometime ago a friend told me that whenever he connected to a two of his SQL Server 2008R2 Servers which happened to be virtual, he was experiencing slowness. At first he thought it was a network related problem, but other SQL Server 2005 virtual Servers on the same host were not giving any problems. All his Servers were default instances and he was not using the standard SQL port. He told me that he checked on Google but he could not find any information on this. Of course I did not believed him, so I did a quick search myself, sadly he was right, there was not really information on the problem, at least not when doing a quick search. His problem was also occurring when making ODBC connections to those Servers.
After realizing that his problem was not going to be solve by my dear friend “Google”, I told him to try to connect to the Servers using the IP-addresses and the port numbers, I always do that when experiencing connection problems and believe it or not, that did the trick. He could work with a normal speed, then I told him to try connecting to the Server using the Server Names and the port and that also worked. He was very happy an me too, but then he asked me why it was happening, I had to tell him that I had no idea, he told me the configuration was the same for all his Servers even the Physical ones and on those he was not experiencing that problem. Since that they I have been trying to figure out what caused his problem, but I have not been able to find an answer. If you happened to know what was causing the problem, please let me know, I will really appreciate it. If you don’t know why, but you are having the same problem, I hope this post may help you to solve it.