Ha Overview; Connectivity And Synchronization Between Devices - AudioCodes Mediant 4000 SBC User Manual

CHAPTER 31 HA Overview
Mediant 4000 SBC | User's Manual
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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.
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.

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.
Thus, under normal operation, one of the devices is in active state while the other is in redundant
state, where both devices share the same configuration and software. Any subsequent
configuration update or software upgrade on the active device is also done on the redundant device.
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