OmniWAN Active and Standby ISP Links are constantly monitored to allow for the usage of the ISPs.
Due to this we do recommend un-metered ISP links for both Active and Standby Links.
However, if a Standby Link is using a metered ISP, such as a LTE or Satellite modem, we recommend at least a 5 GB / month plan to allow for both the data to check the line's availability and any minimal* failover occurrences to the Standby ISP.
*OmniNet recommends customers of metered ISP links clearly understand their vendor agreements to set realistic cost expectations in case of outages. Costs from these providers can be quite expensive so a clear cost analysis should be reviewed by subscribers. Some LTE providers allow a base data plan and thereafter throttle once the monthly data allotment has been reached. In some cases, this may be a better option to avoid costly surprises.