After the primary Kea server has been added to Micetro, it acts as the primary mode of communication between Micetro and the High Availability (HA) cluster. All changes are written to this primary server, whose in-memory config is the single-source-of-truth for the configuration, and replication is handled accordingly. In the event of a failover, the secondary server assumes this role and any changes to the HA cluster should be made to it through Micetro.
- Normal operation
- When both the primary Kea server and all its secondary/backup partners in the
High Availability environment are running and accessible, Micetro reports the Kea DHCP
server as OK.
- Primary server offline
- If the primary server is offline or unavailable for any reason, for example,
reporting itself in a disabled state, or becomes unreachable from Micetro, the secondary
server will take over as the primary in Micetro. Micetro will report the Kea
DHCP service as Impaired. During this time, the single-source-of-truth
will be the in-memory config on the secondary server until connection to
the primary server is re-established.
- Secondary server offline
- If any of the secondary servers are offline, replication to all
other servers will still occur, but Micetro
will report the Kea DHCP service as Impaired. When the affected
secondary reports itself as Active again, it will be
automatically synchronized with the single-source-of-truth configuration (the
in-memory config of the primary Kea server).
- Both primary and secondary server offline
- If both primary and secondary servers go offline, Micetro will report the Kea
DHCP service as Service down. All further operations will result in an
error reporting this downtime. All replication is stopped until either the
primary or the secondary servers report themselves as Active. The
first server to become active will be the single-source-of-truth, but the
primary will always override any secondary when it becomes active.
- DHCP server agent offline
- In the unlikely event that the DHCP Agent is offline, all Kea High Availability
information will be momentarily lost. Micetro
will report the Kea DHCP service as Unreachable. As soon as the Agent
comes back online, Micetro Central will attempt to
reconnect to the preconfigured primary Kea DHCP server. After reconnecting to
the primary server, the configuration will be parsed again, the High
Availability setup detected, and replication between servers resumed.
Note: If the DHCP Agent goes offline while using the secondary Kea server (because the primary server was down), the system will not be able to reconnect successfully. Because only the primary Kea server can be added to Micetro, a system administrator must reestablish the primary Kea server to a working state before the system will be able to reconnect.