If you're seeing this in your vmkernel.log at the time of the disconnect it could be related to an issue that will one day be described at the below link (it is not live at this time). We see this after a random amount of time and nothing VMware technical support could do except reboot the host helped.
http://kb.vmware.com/kb/2124669
vmkernel.log:
2015-07-19T08:22:35.552Z cpu0:33257)WARNING: LinNet: netdev_watchdog:3678:
NETDEV WATCHDOG: vmnic4: transmit timed out
2015-07-19T08:22:35.552Z cpu0:33257)WARNING: at vmkdrivers/src_92/vmklinux_92/vmware/linux_net.c:3707/netdev_watchdog()(inside vmklinux)
2015-07-19T08:22:35.552Z cpu0:33257)Backtrace for current CPU #0,worldID=33257, rbp=0x430609af4380
2015-07-19T08:22:35.552Z cpu0:33257)0x4390cf49be10:[0x418029896b4e]vmk_LogBacktraceMessage@vmkernel#nover+0x22 stack: 0x430609af4380, 0
2015-07-19T08:22:35.552Z cpu0:33257)0x4390cf49be30:[0x418029f1e7b7]watchdog_work_cb@com.vmware.driverAPI#9.2+0x27f stack: 0x430609ac3ce
2015-07-19T08:22:35.552Z cpu0:33257)0x4390cf49bea0:[0x418029f44a5f]vmklnx_workqueue_callout@com.vmware.driverAPI#9.2+0xd7 stack: 0x4306
2015-07-19T08:22:35.552Z cpu0:33257)0x4390cf49bf30:[0x41802984f872]helpFunc@vmkernel#nover+0x4e6 stack: 0x0, 0x430609ac3ce0, 0x27, 0x0,
2015-07-19T08:22:35.552Z cpu0:33257)0x4390cf49bfd0:[0x418029a1231e]CpuSched_StartWorld@vmkernel#nover+0xa2 stack: 0x0, 0x0, 0x0, 0x0,