Intermitent HTTP 401 error message in a SSRS load balancing deployment.
In a SSRS load balancing deployment, you get intermitently HTTP 401 error message when you do any action that requires connection from one node to the other RS node
When you access to Report Manager using the balancer virtual name (http://<virtualname>/Reports) , you can intermittently get HTTP 401 error message when you do any action that requires connection from one node to the other
RS node (as run a report with a data source located in the other node or simply when the Report Manager tries to connect to the Report Server Web Service hosted on the other node).
This HTTP 401 error is caused when the request handled by one Report Manager node is back to the balancer and then is handled by the other SSRS node. In this case, the user credentials are not passed to the second node if you are using NTLM authentication. To solve this issue follow the instructions below to ensure that the session established on a SSRS node doesn’t back to the balancer but persists on the same node.
To solve this problem and avoid a double balancing issue:
Open the file “hosts” on both SSRS servers and map the local node IPaddress with the virtual name of the balancer on each server. Follow these steps:
1. On each SSRS server open C:\Windows\System32\Drivers\etc\hosts.
2. If the following entries are not in there please add them:
Other solution for this problem is to configure Kerberos authentication for SSRS.