Page 462 of 488 Configuring MG 1000T survivability and alternate primary controller553-3041-210 Standard 4.00 September 2007• Procedure 120: "Configuring the IP telephony node for Alternateprimary controller" on page 473• Procedure 121: "Verifying the operation of a Voice Gateway Media Cardin an MG 1000T expansion in Survivable Mode" on page 475• Procedure 122: "Retrieving CDR files using XModem" on page 476MG 1000T switch over to Survival ModeIf survivability is configured on an MG 1000T, the following scenarios cantrigger a switchover to Survival Mode:• Automatic Switchover — triggered when the MG 1000T Expansionloses communication with the primary controller and the SwitchoverTime Out (SWOTO) timer expires. This can occur if there is acatastrophic failure of the primary controller, or the IP link is lostbetween the MG 1000T Core and the MG 1000T Expansion.• Manual Switchover — triggered with the Switchover to Survival (SOTS)command in LD 135.Automatic Switchover to Survival ModeWhen an MG 1000T, with survivability configured, loses communicationwith the primary controller, the MG 1000T automatically switches over toSurvival Mode when the SWOTO timer expires.If the IP link is detected as down again before the expiration of the SWOTOtimer, the timer stops, and the MG 1000T remains in Survival operatingmode.The state of communication between the primary controller and theMG 1000T Expansion is monitored by a simple polling mechanism called aHeartbeat.This example illustrates the tasks performed by an MG 1000T Expansionwhen communication with the MG 1000T Core is lost.1 The MG 1000T Expansion attempts to re-establish the connection to theMG 1000T Core. After four re-connection attempts with a pre-defineddelay between each attempt, the SWOTO starts.
