Cisco or Sonicwall routers connected to the 6300-CX receive an IP address from the 6300-CX, but can only send packets for a few seconds before the connection drops.

We've been running into this issue where 6300-CX units are sending out ARP requests with the default 192.168.210.1 IP address instaed of the gateway IP we get as part of the passthrough connection from the cellular network.  I've encountered this issue while working with a Cisco Router and Sonicwall routers.  In these cases, the routers would get a passthrough connection from the CX and work for a minute or so. However, when the CX sent an ARP request to the router to verify the IP and routes, the routers would not respond to the ARP request since the CX sent the ARP request with a source IP of 192.168.210.1. Since the routers weren't responding to the ARP request, the CX would not route packets to the router anymore, since it didn't know which interface/MAC to send those packets to.

Below are some links to articles I found from Sonicwall and Cisco as to why they don't respond to these ARP requests.

http://www.techrepublic.com/blog/smb-technologist/sonicwall-routers-and-dropped-arp-packets/ 

https://supportforums.cisco.com/document/100896/asa-843-arp-response-behavior-change

Firmware versions 17.5.108.6 or higher resolves the connectivity issues.  The 6300-CX will use a gateway IP in the same subnet as the passthrough IP it gives to the Cisco/Sonicwall router for all ARP requests.

You can use the following instructions to upgrade a 6300-CX or 6300-LX to the new 17.5.108.6 firmware:

https://accelerated.com/support/6300_CX/users_guide_web/#par-21

If you do not wish to upgrade the firmware on your 6300-CX, you can work around the issue by adding a manual route into the Sonicwall or Cisco router for the 192.168.210.1 address of the 6300-CX.

Follow the instructions here to resolve the issue by adding a route for 192.168.210.1 to the Sonicwall.  I've also listed some screenshots below of when I added this route to a test TZ300 we have in the Tampa office

https://support.software.dell.com/sonicwall-e-class-nsa-series/kb/sw7587

I do not have an exact walkthough for adding a route for 192.168.210.1 to a Cisco router, but it should be very similar.