This object specifies the ifIdex value of the source
interface to be used for sending INFORM notifications.
The value of this object should be a valid 'ifIndex' value.
This is a global configuration applied for all INFORM
notifications sent by this agent to all the targets. If the
source interface is configured for a specific target using
the value of corresponding instance of
'cExtSnmpTargetAddrIntIfIndex', then that value takes
precedence and will be used for sending the notification.
The value of this object being 'zero' implies that there is
no source interface configuration for the INFORM
notifications at a global level.