“Cannot generate SSPI context” error message, when connect to local SQL Server outside domain

“Cannot generate SSPI context” error message, when connect to local SQL Server outside domain

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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

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  • Please add 7 and 3 and type the answer here:
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  • Yes, Connecting as localhost\sqlexpress solved the problem. Thanks a ton.
  • Hi,
    I am having the same problem, and the issue here is that the user is using the Win XP and the SQL serve is Hosted on Win 2000. The user is in a seperate doamin and the server is as well. The rights have been given to the user within the SQL server for access. When the user tries to access one server he is able to without any problems, but when he tries to connect to other server in same donain he gets this SSPI error.

    Hopy you can help me on that.

    Regards,
    Himanshu Nirmal
  • Hi,
    I am facing this problem over VPN, I am not able to connect my SQL Server hosted at Different Domain. While connecting with SQL Server Client, it is giving me same error "Cannot generate SSPI context". Please update me. What is the actual process has to be follow to get resolve this issue.
  • Hi, Mahesh

       It seems
    your client box is in a seperate domain, normall, you need configure the two domains ( one your client box in and the other your server box in)mutual-trusted, and you need to make sure the account that running under your client app is same as the service account that your SQL Server is running and both of them have administrator permission either in the domain(if it is a domain account) or in the local box( if it is a computer account).

    Good Luck!
    Ming.
  • I checked the system log and was told the SPS server could not connect to a timing/clock computer...

    I ran the net time command to sync the SPS server time with our domain server and that eliminated the problem.

    net time \\<ip or computer name> /SET /Y

  • Incorrect DNS can lead to various network connectivity issues. In this post, I explain how it affects

  • This post provides some tips to troubleshoot Sql Server connection problems based on various displayed

  • “Cannot generate SSPI context” error message, when connect to local SQL Server outside domain

  • This happens to me, and anything you say does nothin, neither syncronizing time nor doing the other things.

  • Dove,

     Can you describe what is your configuraiton, including machine, account, connection string, sql server and etc. and when it connect, when it dosn't. There could be ton of reasons. Without your input, we don't have clue to help you out.

    Nan Tu

  • Excellent!  Using 127.0.0.1 as my server instead of my computer name solved my issue.

    Thanks!

  • I'm having this error in a different situation:

    If I'm trying to run:

    osql -S 127.0.0.1 ... then I get the error but if I run:

    osql -S <name> ... then I don't

    The machine is a domain controler Win2K with SQL 2K on it - all latest patches applied.

    Any clue?

  • Thank you!!!  This worked (and now I understand why) on an ODBC connection for a Crystal Report.  

  • Changing the database name to 127.0.0.1 (using the default SQL instance) fixed it! Thanks for the excellent post; it saved my life while I was disconnected from the mother ship.

  • I want to give you a big hug!!!  I've been fighting this thing all day and its was making me crazy... now it's fixed!

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