I'm wondering if anyone has configured a 4G backup on a SRX220? If so or if you think you know, what is the best way to do this? This there a card that my client can purchase that can be inserted? (ie use the mini-PIM slots etc).
I dont think there is a mini-PIM for the SRX220 that will provide you a backup 4G connection, however there is an external Ethernet-based 3G/4G LTE bridge for terminating 3G/4G LTE wireless WAN data for SRX Series, see page 2: