Ha Overview; Connectivity And Synchronization Between Devices - AudioCodes Mediant 500 E-SBC User Manual

User's Manual
31

HA Overview

The device's High Availability (HA) feature provides 1+1 system redundancy using two
Mediant 500 E-SBC 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:
sending a SIP BYE message to the IP side). This is because only the active device is
physically connected to the PSTN interfaces. For more information, see Device
Switchover upon Failure on page 512.
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.
31.1

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.
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.
Version 6.8
Only IP calls are maintained during a switchover; PSTN calls are dropped (by
Figure 31-1: Two Devices in HA State
511
31. HA Overview
Mediant 500 E-SBC