WAN Link Failover - if link is down after a dedicated downtime

Question

Hello Community, i've established an XG firewall in a two stage/vendor security area directly at the ISP connect. This configuration is placed in a remote location and i hope, the following challange is possible. My challange Is there a possibility to configure a celluar device at the XG firewall for the following challange - the celluar device is by default offline (not connected to the 3G/4G/LTE network. 
 - if the primary cable connect is down for more than xxx seconds, the celluar device shift to online (dial-in) and overtake the connectivity and serve avalibility of local VoiP/FoIP devices until the issue is solved and the primary link is online. 
 - the celluar device should go offline (disconnected), if the primary link is back and working. Is that possible, or is it only manually possible? Thanks forward Christian

LuCar Toni · Accepted Answer

By default offline is not possible. You can use the other interface as "Backup". 
 In this process, the Cellular will only be used in case the active connection is offline OR you address a firewall policy to use this interface. 
 You can setup everything but not with a "offline" cellular, it will always be logged in and communicate couple of packets (basic keep alive).

ChrisGER · Answer

Thanks for the quick response, is there a matrix of "supported" or "tested" USB dungles for XG firewalls ? in another post is written ".... the dongle needs to be compatible to Linux in order to operate on XG" 
 Is the Linux support the requirement for usage at XG Firewall ? 
 Thnks and best regards Christian

LuCar Toni · Answer

There is a list, but most likely it depends on "your luck". 
 http://docs.sophos.com/nsg/sophos-firewall/17.5/Help/en-us/webhelp/onlinehelp/nsg/sfos/concepts/USBCompatibilityList.html

Manufacturer

Modell

Vendor

3G Standard

Default ID

Modem ID

Protocol

Compatibility

Huawei

E3276

LTE CAT4

12d1:14fe

12d1:1506

Serial and NCM

Probable

Huawei

E3276s-150

LTE CAT4

12d1:14fe

12d1:1506

NCM

Probable

Huawei

E3276s-150

LTE CAT4

12d1:157c

12d1:1506

NCM

Unlikely

Huawei

E3276s-150

Swisscom

LTE CAT4

12d1:1597

12d1:1598

Serial and NCM

Unlikely

As you can see, there are models with the same revision but different compatibility. Unfortunately, most of the time, on the box of the LTE Modem, there is no reference of the Default / Modem ID.