Mike's PBX Cookbook

Survivable Media Gateways

Survivable Media Gateway (SMG) is a feature of Geographic Redundancy (from Release 5.0), whereby a Media Gateway can register with an Alternate Call Server (AC1 or AC2) in the event of the Primary Call Server not being reachable. This maintains (some) service in the event of an equipment or WAN outage. Ideally, an SMG will have some local trunking. See also MGC Geo-Redundancy.

Geographic Redundancy

During normal operation, all MGC's are registered with the Primary Call Server.
Switching between Primary and Alternate Call Servers requires the MGC(s) to re-boot!

Call Server Configuration

The Primary Call Server customer database is automatically replicated to the Secondary Call Server(s), thus all the Call Servers are identical (see note). Per schedule, a compressed EDD backup is sent via SFTP (or FTP in Rel.5) to each SCS, where it is unzipped, restored, and sys-loaded. Database moves, adds, and changes should normally only be performed on the Primary Call Server.

Note: System-specific data, such as IP addresses, netmasks, routes, and nodes, is included in the replicated database but is filtered out and not restored on the Secondary Call Servers.

Database Replication Rule (BKPR)

Databases replication rules and schedules are defined in LD 117.

CHG BKPR xxx aaa ip yy
Add (or change) a backup rule, where:
xxx = backup rule number ID = 1-100
aaa = rule type.
  • SCS = Secondary Call Server
  • FMD = Fixed Media Device
  • RMD = Removable Media Device
  • FTP = File Transfer Protocol
  • USB = Removable USB device
ip = ELAN IP address of the destination system.
yy = the number of database versions to save on the destination system = 1-(2)-10.
OUT BKPR xxxRemove backup rule xxx
PRT BKPR xxxPrint backup rule xxx, or all if blank

For example: NEW BKPR 1 SCS 2 SITE_02

Print configured Backup rules: prt bkpr

=> prt bkpr 

Number of Backup Rules defined = 3
 NN   Dest Parameters           N-of-vers Name
   1  SCS              2     SITE_01    a Secondary Call Server
   2  SCS              2     SITE_02    another Secondary CS
   3  FTP             10     BACKUP    FTP server for backups


Database Replication Schedule (BKPS)

Databases replication rules and schedules are defined in LD 117.

Add (or change) a backup schedule, where:
xxx = backup schedule number ID = 1-10
yyy = number of the backup rule for the scheduled backup operation.
FREQ = frequency, either M = monthly, W = weekly, or D = daily
OUT BKPS xxxRemove backup schedule xxx
PRT BKPS xxxPrint backup schedule xxx, or all if blank

Print configured Schedules: prt bkps

=>prt bkps

Number of Backup Schedules defined = 3
 NN   Backup-Rule   Frequency   Day  Hour  Minute
 1          1       Daily             1      0       site 1, daily at 1 am
 2          2       Daily             2      0       site 2, daily at 2 am
 3          3       Monthly     1     3      0       1st of a month at 3 am


Manual database replication

The database replication and restore procedures can be manually executed with LD 43.

BKR xxInvoke database-replication operation, where:
xx = Backup Rule number.
RSR xx yyRestore the database, where:
xx = Restore Rule number on the local system.
yy = database version number. If no version number is entered, the most recent backup (1) is used.

This command is typically entered on the Secondary system to restore a database received from the Primary system. Filtering of Primary system specific data (YES) must be used.

System status

The status of each system in the Survivable Media Gateway configuration can be obtained in LD 135. On the Primary system, the system status identifies when the last successful database replication was completed, as well as whether the replication process is operating properly.

On the Secondary system, the system status identifies the Secondary system operating state, as well as the time and date of the last successful restore and sysload operations.

Obtain the system status for Primary or Secondary systems in LD 135 as follows:

STAT GRThe current status of Survivable Media Gateway on the specified system appears.
STAT IPL xxStatus of the IP link for a specified MG, and indicates if it is registered to an Alternate CS, where:
xx = cabinet number of the Media Gateway queried.

Note: Use the STAT IPMG command in LD 117 for more details, such as IPMG registration status and uptime.

SMGR xx yyForces Media Gateway to register on a specified Call Server, where:
xx = specified Call Server. eg: PRIM (Primary), ALT1 (Alternate CS 1), or ALT2 (Alternate CS 2).
yy = cabinet number of the Media Gateway to be switched.

An MG forced to switch to a Secondary Call Server remains registered to the Secondary Call Server until it is forced to register back to the Primary Call Server with the SMGR PRIM <cabinet number> command.

The status of each SMG is found on each SMG in LD 135. If a backup attempt fails, a message appears when the Primary system status is printed (using the STAT GR command in LD 135). In the example below, SITE_2 is off-line.

.stat gr

Geographic Redundancy Status
Primary Call Server
Automatic Replication Backup defined: SCHD
Last Successful Replication Backup to
  mode:                Automatic
  Backup Rule number:  1
  Secondary Call Server name:  SITE_01
  performed at:        01:07 on 03 13, 2014
Failed Backup attempts: 1, last one at:  02:14 on 03 13, 2014, to *
Test activated: None
Internet phones registered locally: 0
Media Gateways registered locally: 20
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