Libra Esva network is unreachable after a Microsoft Hyper-V failover.
Use static MAC addresses with failover clustering!
Libra Esva Virtual Appliances that will be deployed using failover clustering should be configured with a static media access control (MAC) address for each virtual network adapter. In Libra Esva (and all other linux kernel based VM) the networking configuration may be lost after failover because a new MAC address is assigned by Hyper-v to the virtual network adapter. To avoid losing the network configuration, ensure that each virtual network adapter has a static MAC address. You can configure the MAC address by editing the settings of the virtual machine in Hyper-V Manager or Failover Cluster Manager.
If you have dynamic MAC on you Libra Esva and if you already experienced the problem the solution is to read the old MAC address from Esva console and force Hyper-v to use this.
Login via console with user admin and select option 3. Show network device info and take note of the MAC address.