Topics from the Microsoft SQL Server Protocols team - Netlibs, TDS, SQL Browser, etc.
The “Cannot generate SSPI context” issue is described by http://support.microsoft.com/?id=811889 in general. In this post I will discuss one daunting case of “Cannot generate SSPI context” error message when failing to connect to SQL server. In most related cases, customers report this issue as "I can connect to my local SQL Server, but once I connect to my network, I can't connection to my local SQL Server". Such issue is reported against MSDE and SQLExpress. But actually, it can happen with any SKU of SQL Server, including SQL Server 2000 and SQL Server 2005, that support NT integrated authentication. The error message for the failed connection that we discussed here is
[SNAC] “[SQL Native Client]SQL Network Interfaces: The Local Security Authority cannot be contacted.[SQL Native Client]Cannot generate SSPI context”[MDAC] “Cannot generate SSPI context”;[.Net1.0/2.0]” Failed System.Data.SqlClient.SqlException: Cannot generate SSPI context”
It can happen when all of followings are true:(1) The hosting machine of SQL Server is connected to a network, including home network or dialup connection, but it is disconnected from its domain.(2) The OS of the hosting machine is Windows XP or 2000. Not windows 2003.(3) The connection is to a local SQL Server.(4) Connection configuration causes network library to choose TCP/IP provider.
A scenario that meets all of (1) (2) and (3) looks like an extreme corner case. But the reality is that it is quit often if the hosting machine is a laptop computer. One solution, of course, is to avoid condition (1) by connecting to your corporate domain through VPN or disconnecting from network completely. The reason why they work is subtle and I’ll discuss it later. From user’s perspective, however, in many cases, either connecting over VPN or disconnecting from network might prevent you from accessing some valuable resources, so I want to discuss solutions that do not depend on (1) first.
In most cases, users do not explicitly require TCP/IP as the connection provider. For example connection strings in form of “.\<instance>”, “(local)\<instance>”, “<servername>\<instancename>” are among them. Users might wonder why network library chooses TCP/IP provider instead of Shared Memory provider, if the connection string is not prefixed with “tcp” and the server is local. A simple answer is that it can happen if the TCP/IP provider is in front of other providers in the client protocol order list, or/and the local server is not listening on Share Memory and Name Pipe. As described above, only TCP/IP provider has the issue; hence, configuring network library not to choose TCP/IP is a solution. To do that, first, on the server side, make sure your server is listening on Shared Memory or/and Named Pipe connection requests; then, on the client side, change the protocol order list such that Shared Memory and/or Named Pipe are in front of TCP/IP, or prefixing your connection strings with “lpc” or “np” to force Shared Memory or Named Pipe, or using alias that prefix Named Pipe in connection strings, whichever you feel most comfortable with. Note that certain SKUs of SQL Server have named pipe connection turned off by default.
In very rare case, however, if you really in need of TCP/IP connection, the option is to use TCP/IP loop-back address, i.e. “127.0.0.1”, as your <servername>. For example, if your connection string has form of “<servername>\<instancename>” and is not prefixed with “tcp”, without modifying the connection string, you can configure an alias with alias name as <servername>\<instancenane>, protocol as TCP/IP, server as “127.0.0.1\<instancename>” or “127.0.0.1,<port>”. Remember that the “Cannot Generate SSPI context” problem described in this post only happens when connecting to a local server; thus, the “127.0.0.1” is applicable. If the connection string is prefixed with “tcp”, then you do need to modify your connection string to specify “127.0.0.1” as <servername>.
If these workarounds described above do not fit your needs, we would like to hear more from you.
The reason that we didn’t fix this subtle issue is because the limitation is rooted in a behavior of an integrated authentication module (SPNEGO) in XP and windows 2000, i.e. whether to fallback to NTLM if KDC is not available when the target SPN points to local machine. KDC, normally, is part of your domain controller. For this specific case, SPNEGO chooses not to fallback, hence connection fail. This issue is not a security issue though. Reader might ponder why avoiding using TCP/IP provider can solve the problem while explaining it is because certain behavior of SPNEGO in Windows. Not going too deep, the simple answer is that only TCP/IP provider, with an exception of loop-back connection, uses SPNEGO while other providers use NTLM. Be aware that only TCP/IP provider can provides the benefits of Kerberos authentication as discussed in http://blogs.msdn.com/sql_protocols/archive/2005/10/12/479871.aspx
Back to the questions we left before, the reason that disconnected from network (no network media) works is because, in such case, local <servername> is resolved to “127.0.0.1” by windows network layer and NTLM is used directly. When connected over VPN, the SPNEGO issue goes away because the KDC is accessible in this case.
From the error message reported by SNAC ODBC/OLEDB, you can differentiated the issue described by this post from another case of “Cannot generate SSPI context”, in which the root cause is because, in Active Directory, the Service Principle Name (SPN) of SQL Server is registered for a domain account different from the SQL Server is actually running under. The error message for the other case is “[SQL Native Client]SQL Network Interfaces: The target principal name is incorrect.[SQL Native Client]Cannot generate SSPI context. The “Cannot generate SSPI context” issue is described by http://support.microsoft.com/?id=811889 in general and by http://blogs.msdn.com/sql_protocols/archive/2005/10/15/481297.aspx specifically for the other case.
Do you know that you can post question w.r.t SQL Server data access, connectivty issues at http://forums.microsoft.com/MSDN/ShowForum.aspx?ForumID=87&SiteID=1 ?
Nan Tu, Software Design Engineer, SQL Protocols
Disclaimer: This posting is provided "AS IS" with no warranties, and confers no rights
iam using the Win XP and the SQL serve is Hosted on Win 2000...i keep getting disconnected from SQL D.B every hour and SSPI context error shows up...i log off the pc then log in again and then i can log in to the D.B again...how can i stop it plz?
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I installed SQL Express in Windows server and tried to connect with it, getting this error...but it connects with the SQL authentication...when I tried to connect it with Windows authentication. I'm getting this error.....plz help me
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I'd like to script this so I can ensure Named Pipes is enabled on the SQL 2008 server and the SQL 2008 client has named pipes enabled and the order is BEFORE tcp/ip. How can I script this? Not finding it in sp_configure..
Please reply or email email@example.com
I disabled TCP/IP, enabled Shared Memory, and Named Pipes options from SQL Server Configuration Manager on my Microsoft SQL Server 2005, restarted the Server. I was able to get out of this error. Thanks a lot to this posting.
Please help me out!! I have been trying to connect but getting this error msg "Cannot generate SSPI context". I need a access a BAK file on server using SQL.
i have ms access based application linked to ms sql server. when i try to connect this application through a client machine (winXP), i am getting unablae to generate SSPI context error. but in the same machine, when another user log in he is able to connect to server without problems?
is there a possibility that this problem is linked to user account?
I just experienced this error again, on a computer that is a member of a domain, but where the computer is disconnected from the network.
The error occurs not only when using the TCP/IP protocol, but also when using Shared Memory (I tried disabling all other client protocols and also all other server protocols).
The error I get, when trying to use the osql.exe utility, to connect to the server, looks like this:
[SQL Server Native Client 10.0]SQL Server Network Interfaces: The Local
Security Authority cannot be contacted
[SQL Server Native Client 10.0]Cannot generate SSPI context
The computer has a loopback interface which allows it to still use TCP/IP, but doesn't allow it to connect to anything.
The only workaround that has worked on this computer has been to enable the TCP/IP protocol again and connect to 127.0.0.1/InstanceName instead of using .\InstanceName or ComputerName\InstanceName.
Superb , it helped me solved my problem in Biztalk
I have just experienced this error and the problem was in the server where SQL Server instance was running because the time in Operating System was not correct and assincronous from the Active Directory server time. The error was solved fixing the time in the operating system where SQL Server was running.
im facing problem cannot generate sspi context after some time the application is open. once i logged off and login again, im able to connect for some duration, again it will raise the same error message.
Please guide me on this
Bless you! I'm the classic laptop software professional, with a domain in the office, and no domain at home. Changing my code from my laptop's name to 127.0.0.1 was the trick.