WIFI Router Connected to ATT Mifi One Laptop Locks-up ATT Mifi

[cruzmoan]

I have an ATT 5G Mifi device.  My Netgear R9600 router is connected to the mifi device via a LAN cable.  All devices in my home can connect to this setup fine and browse the web.  I have one laptop that when it connects the ATT 5G Mifi device locksup and all other devices nolonger have internet access, including the offending laptop.  The offending laptop's wifi connection is managed by the Cisco AnyConnect client.  Any ideas why this laptop locks-up the 5G Mifi? Thanks in advance!

[FURRYe38]

Your ISP Modem already has a built in router and wifi. This would be a double NAT (two router) condition which isn't recommended. This would be a double NAT condition which isn't recommended. https://kb.netgear.com/30186/What-is-Double-NAT
https://kb.netgear.com/30187/How-to-fix-issues-with-Double-NAT
Couple of options,
1. Configure the modem for transparent bridge or modem only mode. Then use the NG router in router mode. You'll need to contact the ISP for help and information in regards to the modem being bridged correctly.
2. If you can't bridge the modem, disable ALL wifi radios on the modem, configure the modems DMZ/ExposedHost or IP Pass-Through for the IP address the NG router gets from the modem. https://kb.netgear.com/25891/DMZ-on-NETGEAR-routers
https://kb.netgear.com/24086/How-do-I-set-up-a-default-DMZ-server-on-my-Nighthawk-router
3. Or disable all wifi radios on the modem and connect the NG router to the modem, LAN to LAN configure AP mode on the NG router.
https://kb.netgear.com/20927/How-do-I-change-my-NETGEAR-router-to-AP-mode

Try option #2 first. 

Might ask the ISP about this as well regarding there product...