A small heads-up on something which you need to configure when deploying a Highly Available setup of physical or virtual KEMP LoadMaster devices in environments with redundant network routing components, but this may apply to other components with similar functionality as well. While in typical environments the LoadMaster’s default setting will never be an issue, it can easily be overlooked or not immediately considered suspect when you do have issues, for example in hosted environments.
Note: If you are looking for more information on load balancing Exchange 2013 using KEMP LoadMaster devices, Exchange-fellow Jeff Guillet did an excellent multi-part write-up on this topic here.
When configuring multiple LoadMaster’s in a High Availability setup, one of the settings is the HA Virtual ID parameter, which is located System Configuration > Miscellaneous Options > HA Parameters. This setting configures the routing identifier used by the LoadMaster as part of the VRRP or Virtual Router Redundancy Protocol (see RFC5798).
The HA Virtual ID is used to construct a unique MAC address, so that all devices in the same VRRP group can communicate. The MAC address uses a format as defined by VRRP, and is 00:00:5E:00:01:<ID> for IPv4 and 00:00:5E:00:02:<ID> for IPv6. One device, the Master being the Active LoadMaster, owns the VRRP group and manages its MAC address and shared IP address.
As you can imagine, using the same identifier for multiple non-related devices on the same segment may cause unexpected behavior, like LoadMasters being unable to communicate with eachother, both HA LoadMasters thinking they are the Active HA node, or other disruptive behavior. This is likely caused by a device other than LoadMasters managing the VRRP group.
Therefor, it is recommended to always change the default value of ‘1’, but always consult with the network or hosting people which value to use, as different vendors use their own default ID. For example, Cisco may use a different default value than FortiNet or CheckPoint for their redundant networking components. Of course, you also need to use different values when using multiple HA LoadMaster deployments on the same segment.