Brian H. Madsen
Computer says no

SSRS 2008 Add-in for MOSS 2007, Report Viewer 401: unauthorised error

June 15th 2009 in 5700, 8761, 9429

Battling with network issues can be a PITA – battling with network issues AND application errors is a FPITA!

A problem popped up the other day with the Report Viewer, while selecting a report to display in the SQL Server 2008 Report Viewer web part.


We could run the Report Viewer web part on the server itself, but from anywhere else on the network it just didn’t work and it kept throwing this error:

Server was unable to process request. —> The request failed with HTTP status 401: Unauthorized.


Rather annoying so we thought the proxy was causing the problem..but, nopes, doesn’t seem like that was the issue as we were told that the internal servers, if addressed via fully qualified domain names, didn’t get proxied.

ok…what else to do? some suggested Alternative Access Mappings were wrong…tried to add what was “missing” there..still a no go.

It was obvious that something was dropping off the authentication request somewhere as we were running in “Windows Authentication” mode, using NTLM.

fix was…

Go to the SharePoint 3.0 Central Administration –> Application Management –> Reporting Services –> Manage Integration Settings and change the Authentication Mode to “Trusted Account”..

rep-serv-mng-int authmode-trusted

Now, of course, i need to find out why Windows Authentication mode isn’t working…at least we can proceed now.

5 comments to...
“SSRS 2008 Add-in for MOSS 2007, Report Viewer 401: unauthorised error”

Daniel O

Isn’t it just a double hop issue? Windows Authentication would be passing on the user’s impersonated credentials – which won’t work unless Kerberos is setup.

Changing to Trusted Account means SharePoint would be creating the credential on the SharePoint server so it’s only hopping once.



that’s what i thought at first – but it’s actually passing on the details correctly (well, partly obviously).

something else is going on with that server – i’ll figure out eventually what it is but for now, we run in trusted account mode :)

Koen Vosters

Did you disable the loopback on IIS? As that error pops up on SharePoint and search



Nopes – didn’t think of that..will try that out tomorrow as well.

thanks for the tip.


hello Brian, could you explain, how do you resolved why Windows Authentication mode isn’t working? a little step-by-step explanation :) thank you


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