I've seen if the cell device (USB connected) is in a spare MX it will sit in Ready Status until it connects. Once active (wan link failure) you see the active IP address. Not sure if that's a hard and fast rule as I just ran a report and every cell card in Ready status has an IP at the current moment ;). Connecting.... Is the one we watch out for, if they are in this status its hit and miss if they will come active when needed.
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