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Single sign-on prompts for multiple logons across servers

This tip describes how to stop multiple logins when SSO was set up on multiple servers.

After a few months of setting up a client's environment with three Domino servers and a Sametime server, we started to notice that one of the servers started having SSO issues causing us to log in multiple times.

The clients log into a common, multi-server hostname:, which is setup in DNS to point to all three mail servers. This would prompt the user to log in and based on a PAB lookup, redirect to the appropriate mail server and mail file. We'd noticed that occasionally one of the three servers would give us the "Session Expired" error and force our users to login a second time.

After chasing down the error with the Knowledge Base, forums and even with support, I still had no answer. Then it hit me: Could the system time on the server have anything to do with it? All the servers used the good old MS "net time" sync in the login script. But like everything else, even if it's installed, is it running and running correctly?

Nope! One of the servers (the one with the issues) was four seconds off. It couldn't that simple, could it? Yep! The time was only synched when someone logged in. After installing a REAL time synch program (D4 from, all the servers were set to the exact same time (updated every 15 minutes, not once a month) and the SSO issue disappeared!

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