When you have a Kemp 360 Central HA pair deployed in a Metered Licensing environment, both units must be running the same version of Kemp 360 Central. If you upgrade one unit in the pair, you must upgrade the other unit as soon as possible to maintain consistent HA operation.

For Metered Licensing HA, Kemp 360 Central checks that the following are true at every HA poll:

  • Both units have the same local license setting – that is, they are either both licensed for local licensing or are both not licensed for local licensing.
  • Both units have the same Metered Licensing license setting – that is, they are either both licensed for Metered Licensing or are both not licensed for Metered Licensing.
  • Both units are running the same version of Kemp 360 Central.

If any of these values are not true, Kemp 360 Central returns an error and moves itself into standalone mode (that is, out of HA mode).

The most likely reasons for this occurring are: one of the HA units’ license was updated or a backup was restored to one or both of the units, which resulted in a licensing mismatch between the units.

Managed LoadMasters can grab a license from either Kemp 360 Central unit and can re-license against either unit; the license then ‘migrates’ from one Kemp 360 Central unit to the other. Note that if the LoadMaster re-licenses from both units in quick succession, both units may indicate that the LoadMaster is licensed by the other unit. This can be addressed by re-licensing the unit again, and then waiting a few minutes for the re-license to synchronize across the pairs.

Metered Licensing reports from either HA unit contain all Metered Licensing LoadMasters licensed across both Kemp 360 Central HA units. A unit licensed against the ‘other’ peer is indicated in the Metered Licensing report by including the device ID from the other Kemp 360 Central HA unit in parentheses:

If one of the Kemp 360 Central HA units in a pair is removed from the HA pair, all actively licensed LoadMasters are moved to the other Kemp 360 Central unit as ‘normal’ (that is, not activated by Kemp 360 Central) devices. These units must be re-licensed against the remaining Kemp 360 Central unit. To do this, you must:

  • Remove the existing normal (green) unit from Kemp 360 Central.
  • Re-license the LoadMaster from the LoadMaster web user interface (UI) against the remaining Kemp 360 Central instance.

In releases before Version 1.23, it was not possible to take a backup from one HA unit (for example, the Master) and use it to replace the other unit (the Standby) in the HA pair; this broke the HA configuration.

In Version 1.23 and later releases, doing the above no longer breaks the HA configuration, but you must still check that the Disable, Preferred Master, IP Address for the Other Peer, and HA Key for the Other Peer settings are correct for your configuration. That is, under normal operation, neither unit should be disabled, only one unit should have the Preferred Master option selected, and the IP Address for the Other Peer and HA Key for the Other Peer should contain information obtained from the UI for the other unit in the HA pair.