FYI, I have had this happen twice to one of my cluster hosts, about a week apart. My hosts are Dell Poweredge R710 servers, and this is happening with a clean install and configuration of ESXi 6.0 on both of them. I sent my logs into VMWare support and was told the following:
We see " LinNet: netdev_watchdog:3678: NETDEV WATCHDOG:" alerts in vmkernel logs, which is making the host loosing connectivity. This is a known BUG in ESXi 6.0 and currently we do not have any resolution for this. The temporary fix is to reboot the host so that it can recover the network settings.
For now we are recommending to rollback to ESXi 5.5 ( http://kb.vmware.com/kb/1033604>Reverting to a previous version of ESXi)
Just thought I'd pass along this info for anyone else that encounters this error and comes searching for it. I just received some instructions from VMWare support because they want to gather some debug logs to try and track the issue down. I'll update this thread with more info if I get it.
wally