Version 7.2 803 Mediant 800B Gateway & E-SBC
User's Manual 41. HA Overview
41 HA Overview
The device's High Availability (HA) feature provides 1+1 system redundancy using two
devices. If failure occurs in the active device, a switchover occurs to the redundant device
which takes over the call handling process. Thus the continuity of call services is ensured.
All active calls (signaling and media) are maintained upon switchover.
Note:
• Only IP calls are maintained during a switchover; PSTN calls are dropped (by
sending a SIP BYE message to the IP side). This is because only the active
device is physically connected to the PSTN interfaces (e.g., E1/T1). For more
information, see Device Switchover upon Failure on page 804.
• HA is supported only on the Mediant 800B hardware platform (not Mediant 800).
The figure below illustrates the Active-Redundant HA devices under normal operation.
Communication between the two devices is through a Maintenance interface, having a
unique IP address for each device. The devices have identical software and configuration
including network interfaces (i.e., OAMP, Control, and Media), and have identical local-port
cabling of these interfaces.
41.1 Connectivity and Synchronization between Devices
In HA mode, the Ethernet connectivity between the two devices is through a special LAN
interface on each device, referred to as the Maintenance interface. Each device has its
own Maintenance interface with a unique address, and each device knows the
Maintenance address of the other. The Maintenance interface can use a dedicated
Ethernet port group or share the same Ethernet port group with the other network interface
types (i.e., OAMP, Media, and Control).
When only one of the devices is operational it is in HA stand-alone state. This means that
the device has no connectivity to the second device. When the second device is powered
up, it recognizes the active device through the Maintenance network and acquires the HA
redundant state. It then begins synchronizing for HA with the active device through the
Maintenance network. During synchronization, the active device sends the redundant
device its current configuration settings, including Auxiliary files. The active device also
sends its software file (.cmp) if the redundant device is running a different software version.
Once loaded to the redundant device, the redundant device reboots to apply the new
configuration and/or software. This ensures that the two units are synchronized regarding
configuration and software.
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