Not sure if any of this is 100% network related. There is an issue with HBA's disconnecting, and with 5.1 if hosts lost connection to Storage will also be in disconnected state.
Need to enable SSH on ESX host, and make sure SSH ports open on Firewall of ESX host. Then can connect via SSH and PUTTY.
Enter command:
esxcli system settings kernel list -o iovDisableIR, will show status…if it is False will need to run next command to set to true:
esxcli system settings kernel set --setting=iovDisableIR -v TRUE
Then need to reboot to enable setting on Host. Could re-run first command after reboot to verify settings.
Please see VMware KB 1030265