I recently discovered that not all of our servers are in sync with our internal NTP server that resides on our Server 2012 R2 Domain Controller. We recently moved from Server 2003 to 2012 about 4 months ago. We have a mixed server environment including Servers 2003 R2, 2008, 2008 R2 and 2012 R2. Everything worked fine with 2003. All of our 2012 servers sync with no problem but only some of the 2003 and 2008 are in sync. I also should state that these are all virtual servers. I made sure all the VM tools were up to date and that the most current Windows updates were completed but for some reason, some of the servers won't sync. I've tried forcing sync via CLI in command prompt and I made sure that the virtuals were in sync with their host which I resync'd in vSphere. Does anyone have an idea how I can get this to work throughout my entire server farm? Also, we have two RHEL4 servers that pointed to the 2003 server and stayed in sync but they don't with 2012.