Known Limitations
This section describes the known limitation of the server redundancy function.
Automatic Fallback
After a server failure using automatic fallback to the regular server, fallback will take place when the server is functioning again. This can create problems if the regular server starts and stops repeatedly during a short period of time.
Several regular servers failing at the same time
If there are more than one faulty regular servers in a cluster, the standby server will only replace one of the faulty servers. Other faulty servers will not operate. Which of the faulty regular servers the standby server will replace depends on the regular servers priority to run on the standby server. If they have equal priority the first started on the standby server will continue to run. Only servers with higher priority will replace an already running server.
Limitations when a LIM is running on the standby server
The management system, running on the primary server, is not started on the standby server.
The CSTA Phase III Web Service Application function, possibly running on the primary server, is not started on the standby server.
Other Consideration
The base IP address of a server in a cluster is used for connecting to applications on the specific server.
The alias IP address of a server in a cluster is used for applications moved between regular and standby server.
For more information on when to use base and alias addresses, see the installation instructions for INSTALLING AND CONFIGURING MIVOICE MX-ONE.
For IPv4 Gratuitous ARP is used to update ARP caches when an alias IP address is moved between a regular server and the standby server. Routers and switches have to be configured to accept Gratuitous ARP.
If Gratuitous ARP is not accepted, the failover time will equal the ARP cache timeout time, which is normally not acceptable.
To prevent too long delay in the failover, the ARP cache timeout time should not be too long. Gratuitous ARP is sent periodically to make sure network caches are updated.