We are using an 802.1x configuration policy that uses AD computer certificates to get on the network. It generally works as can be expected. Every now and then I'll get a call from users who suddenly can't get on the network. When I look at System Preferences > Network and click on the Connect button I am prompted to pick a certificate and there are 2 certs with the computer name: ComputerName and ComputerName(1) When I look in Keychain Access> System> Certificates sure enough there are 2 certs for their computer. The first one has NOT expired and the second one indicates it was created shortly before the user lost connectivity with the network. I delete the old cert and make sure the new cert lets them on the network. My question is where do I begin to look to troubleshoot this? is it a Mac thing? a configuration policy thing? a Certificate server thing? It's happened a few times to a handful of users, but not at the same time. I can't find anything in the logs at the time it happens. Previously I thought maybe the user is doing something to make it happen, but it just happened to me this morning on my admin Mac and I was definitely not doing anything with the certs or keychain at the time.
