If the HA status is showing as master/master or suppressed mode, there are some things that can be checked:
- Confirm that multicast is allowed on the network.
- Confirm that IGMP snooping is disabled.
- Ensure that promiscuous mode and PortFast is enabled
- For Virtual LoadMasters: ensure that MAC spoofing is allowed (see note below).
Ensure that the vSwitch HA VLAN is not part of the network. This is to ensure that the KEMP HA update does not interfere with the live production traffic while updating HA.
Note for Virtual LoadMasters:
In VMware there are security policies that can be applied to the virtual switches that can prevent a Virtual LoadMaster from properly controlling the MAC addresses for HA. You can find out more about these policies here:
Edit the layer 2 security policy on a vSwitch
Hyper-V has a per-vNIC setting to Allow MAC Spoofing in the Virtual Machine NIC settings - this needs to be enabled. This can be enabled in the Hyper-V Manager GUI or via PowerShell:
Microsoft Technet article