Can not connect to a SQL instance on over the network

Hi,

I am struggling to connect to a SQL instance from SQL management Studio installed on another server. I have been able to do so until recently and it is not clear what may have caused this. Here are the symptoms:

When i try to connect to Server\Instance using SQL management studio, i get "a network related or instance specific error has occured...."

But

When i connect to Server\      (no instance, i.e. default uinstance) it connects no problem.

The server names resolve correctly from both sides and all protocols are enabled in SQL config on both sides.

Port 1433 is open. (1434 is not used in this environment).

Any help would be greatly appreciated.

Thanks

m
mk112233Asked:
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Vitor MontalvãoMSSQL Senior EngineerCommented:
What about SQL Server Browser? Is it running in the target server?
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ste5anSenior DeveloperCommented:
Cause "Server\" works, I guess it's the default instance. So "Server\Instance" is a different instance on the same machine. Here I would guess it's not configured to accept remote connections.

See How to enable remote connections in SQL Server 2008?
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rossgroupdbaCommented:
w/o explicitly supplying the port# of the named instance the SQL driver needs to communicate with the SQLBrowser service on the remote computer to ask for the port# of the requested instance.  SQLBrowser I believe generally runs on port 1434.  When asking to connect to the default instance  the driver 1st attempts on 1433 then I believe will then ask the SQLBrowser unless of course you supply the port#(non-default) of the default instance.

Are there multiple instances?  
Either turn on SQLBrowser  
OR
Check SQL cfg mgr find out the dynamic or fixed port of the named instance
connect in SSMS via <Server>\<Instance>,<port>  if that works and you dont want to use SQLBrowser then I would suggest altering the port to be fixed or next time the instance cycles you will have to lather rinse repeat.
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mk112233Author Commented:
SQL Browser service is running on both servers. The instance is running on port 1433 only according to CQL config on the destination server.
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mk112233Author Commented:
port 1433 is definitely open from the source to destination
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Vitor MontalvãoMSSQL Senior EngineerCommented:
The instance is running on port 1433 only according to CQL config on the destination server.
This is the default port for the default instance. A named instance should have another port number.
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rossgroupdbaCommented:
Are you trying to connect to the default instance or a named instance?
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Microsoft SQL Server 2008

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