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Home > Success Center > Network Performance Monitor (NPM) > NPM - Knowledgebase Articles > Validation of viewstate MAC failed. Invalid viewstate.

Validation of viewstate MAC failed. Invalid viewstate.

Created by Daniel Polaske, last modified by MindTouch on Jun 23, 2016

Views: 1,641 Votes: 1 Revisions: 6


The following error occurs in NPM:

Validation of viewstate MAC failed. Invalid viewstate


NPM 9.5 and later


Windows Server 2008 is not properly configured to serve static content or a load balancer is being used on the primary polling engine or additional Web server.


Refer to Deploying a Static Content Server to configure IIS 7 to serve static content and verify that the following option is selected:

  • Common HTTP Features: Static Content

If the issue is not resolved and a load balancer is being used, refer to:

 Resolving view state message authentication code (MAC) errors.



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