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Problem connecting to SQL Server over firewall

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Igor Marchenko

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Aug 13, 2010, 2:29:03 PM8/13/10
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Hello!

I am troubleshooting connectivity from client computer to SQL Server 2008
named instance. We have opened 1433 and 1434 ports to allow connectivity. I
am able to connect using <SQLServerName>\<InstanceName>,<PortNumber> syntax.
But I would like to connect without specifying port number. SQL Server
Browser service is running on SQL Server. Also, IPall settings in TCP/IP
protocol is configured to use dynamic port in question.
I am not sure if there any other ports that I have to open to allow
connection without specifying port nunber. I am able to connect using
<SQLServerName>\<InstanceName> from clients that don't go through firewall
(for exmaple, inside SQL Server network). That makes me think this is
firewall restrictions.
Any help is greatly appreciated.

Igor

Erland Sommarskog

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Aug 14, 2010, 4:27:17 AM8/14/10
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First of all, which port number is the instance listening on? If you have
set the ínstance to listen on port 1433, you should get away with using
the server name only.

If the instance is listening on another port, you obviously need to open
that port as well.

You should not use dynamic ports, but for the SQL Server instance to listen
to a specified port. Or else you can't know which port to keep open.

When it comes to port 1434, notice that this port should be opened for
UDP, not TCP.

I think in many places they disable the Browser service entirely to decrease
the surface area, and require that connection is done through port number.
And when you think of it, it makes sense. The idea with named instances and
the browser server is to relieve you from having to find a port. But if you
have a firewall in which you open ports, you want to open as a few ports
as possible, why you tie the instance to a certain port. Which kind of
makes the browser service superfluous.

--
Erland Sommarskog, SQL Server MVP, esq...@sommarskog.se

Links for SQL Server Books Online:
SQL 2008: http://msdn.microsoft.com/en-us/sqlserver/cc514207.aspx
SQL 2005: http://msdn.microsoft.com/en-us/sqlserver/bb895970.aspx
SQL 2000: http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx

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