uplink: 0 indicates Internet1 is being used.
uplink: 1 indicates Internet2 is being used.
uplink: 2 indicates Cellular is being used.
When the MX appliance experiences a Ethernet port state change, an "Ethernet port carrier change" "Event type" will be logged under Monitor>Event log. The "Details" of this event define the type of state change and port that was affected. For example, "device: lan0, carrier: false" means LAN1 on the Meraki had a hard down and the Ethernet link was lost. Another example, "device: wan0, carrier: true" means that Internet1 port on the MX was activated after being down. To filter the Event log for these events, deselect everything except Router>Status event. A high number of these events in the Event log could be the result of an interface reset or reboot of directly connected device, bad cabling, or a cable being disconnected. If a reboot is suspected, check the logs or uptime of the directly connected device. If Ethernet connectivity is suspected, verify matching speed and duplex settings and replace the cabling between the MX appliance and the directly connected device.
The MX uses heuristic detection to determine if an Internet link is down. If the Ethernet link state is up but the MX is unable to ping Internet hosts, resolve DNS names of Internet hosts or ARP entries for the default gateway, it will trigger a link failover.