4G Modem Setup

[Peter847]

I have bought a Netgear LB1120 4G modem for a backup WAN to my pfSense box. The modem works as expected when connected to a standard Windows PC but not when connected to pfSense. I set the interface up for DHCP and the modem is in bridge mode. When I plug in the modem, it connects, assigns its WAN address to the interface and all looks ok. But it then disconnects, connects, assigns the IP address again, this repeats every 30 seconds or so. At the same time the CPU load goes from 5% to 80%.

Any thoughts on what is causing this DHCP cycling?

[JKnott]

@Peter847

Fire up Packet Capture to see what's happening. Then we might have a clue.