My personal implementation of uplink monitoring with failover handling.

The failover works by switching the route metric of the secondary uplink between 1 and 1000. Thus, existing default routes must be strictly inside this range.

This script uses the commands ifmetric and conntrack which must exist in PATH.

A text message can be sent on failover/failback, via Netgear LTE modems supported by Eternal Egypt or Huawei modems supported by huawei-lte-api.

See etc/uplink-monitor.yaml.