FxM and FxV appliances on a VLAN become unreachable through eth0. So the HTTP UI and SSH are unavailable.
However FxM and FxV continue to collect and process data while they can not be logged in to remotely.
This was only seen at one customer, but it was caused by switchport security being triggered at the network switch.
It is believed that the VLAN configuration allowed more then one MAC to talk on this port and that triggered security, however after removing the security setting, the issue stopped.
Remove the following security params from the VLAN configuration.
switchport port-security violation restrict