CHAPTER40 HA Overview
Mediant 800 Gateway & E-SBC | User's Manual
■ Failure in active device: The redundant device initiates a switchover. The failed device
resets and the previously redundant device becomes the active device in stand-alone mode. If
at a later stage this newly active device detects that the failed device has been repaired, the
system returns to HA mode. If Preempt mode is enabled and the originally active device was
configured with a higher priority, a switchover occurs to this device; otherwise, if it was
configured with a lower priority (or Preempt mode was disabled), the repaired device is
initialized as the redundant device.
■ Failure in redundant device: The active device moves itself into stand-alone mode until the
redundant device is returned to operation. If the failure in the redundant device is repaired after
reset, it's initialized as the redundant device once again and the system returns to HA mode.
Connectivity failure triggering a switchover can include, for example, one of the following:
■ Loss of physical (link) connectivity: If one or more physical network groups (i.e., Ethernet
port pair) used for one or more network interfaces of the active device disconnects (i.e., no link)
and these physical network groups are connected OK on the redundant device, a switchover
occurs to the redundant device.
■ Loss of network (logical) connectivity: No network connectivity, verified by keep-alive
packets between the devices. This applies only to the Maintenance interface.
● Switchover triggered by loss of physical connectivity in one or more Ethernet Group
is not done if the active device has been configured to a Preempt mode level of 10.
In such a scenario, the device remains active.
● After HA switchover, the active device updates other hosts in the network about
the new mapping of its Layer-2 hardware address to the global IP address, by
sending a broadcast gratuitous Address Resolution Protocol (ARP) message.
Viewing HA Status on Monitor Web Page
You can view the status of the HA system on the Monitor page of the device's Web interface. The
page provides a graphical display of both active and redundant devices, as shown below:
You can distinguish between active and redundant devices as follows:
■ Active device:
● Color of border surrounding device is green.
● Title above device is "Active Device". The default name is "Device 1".
■ Redundant device:
● Color of border surrounding device is blue.
● Title above device is "Redundant Device". The default name is "Device 2".
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