When using DyKnow behind a load balancer for multiple application servers (for information about DNS Round Robin, see this article), you need to set up all Application Servers with the same machine key.
This can be done for all sites in IIS or site by site. If DyKnow is the only server running on these machines, it is safe to set the same machine key for all sites.
To check your machine key:
1. Open IIS Manager
2. In the ASP.NET section, select Machine Key
3. Look at the values under Validation key and Decryption key. If it says "AutoGenerate" you do not have a machine key set.
The screenshot below does not have a machine key set.
To set your machine key for all sites:
1. On the first Application Server, go to the Machine Key section
2. On the right side under Actions, select Generate Keys and be sure to uncheck both boxes.
The following screenshot is set up correctly (do not copy this machine key)
3. Copy these values (both Validation key and Decryption key) to the other Application servers
This is necessary because some components of DyKnow use encrypted cookies using .NET Forms Authentication.