Junos Space Network Monitoring or OpenNMS

Junos Space Network Monitoring (OpenNMS) can handle part “monitor and raise a notification if threshold is crossed”.

SNMP polls for ifInOctets/ifInOctets for specifx ifindex. These polls could be to the specific group of interfaces, not all of them.

OpenNMS Notifications supports “send SNMP Trap” or “send HTTP GET/POST” to specific IP/URL, where off-box script is located .

Then off-bos script can login to the box and apply the config.