Appendix F -Using Ipsec To Create Ip Persistence; The Problem With Multiple Wans - CalAmp Fusion User Manual

APPENDIX F —USING IPSEC TO CREATE IP PERSISTENCE
This application note describes how the Fusion and connected devices can be easily accessed from a remote
application using IPsec tunnels. This method allows for continuous communication even though the Wan IP address
changes when a Fusion's WAN interface becomes unavailable and the Fusion uses an alternate method to access the
Internet.

1. THE PROBLEM WITH MULTIPLE WANS

The Fusion LTE router supports many methods for accessing the Internet. These include either of two cellular modules,
a WiFi module, or potentially any of three Ethernet ports which may be connected to yet another wireless device such
as a narrowband Motorola HPD. The Fusion can be programmed to automatically detect which of these interfaces is
available at any given time and will choose the highest priority interface for sending traffic.
Figure 89 Router Settings – Interface Priority
Traffic originating from within the Fusion or traffic originating from devices connected directly to the Fusion will
automatically be routed out through the active WAN interface and will easily reach its required destination. However,
when the user wants to actively poll or remotely access the Fusion and connected devices, the changing Fusion WAN
interface can pose a problem. As the Fusion switches between one interface and the next, the IP address used to
access the Fusion remotely changes as well. In addition, many cellular accounts will assign the WWAN interface a
dynamic IP address, meaning that the IP address used for remote access will be different each time the unit connects
to the cellular network.
To solve this particular problem, the Fusion allows secure tunnels to be configured and automatically created between
the Fusion and a host server at the user's office or corporate location. This tunnel is automatically reestablished by the
Fusion every time the Fusion changes its outgoing interface or whenever there is an interruption in the cellular service.
As a result, applications residing behind either end of this secure tunnel can continue to have direct access to each
other without needing to know which interface the Fusion is currently using to access the Internet or what IP address is
currently assigned to the Fusion's WAN interface.
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Fusion Multi-Network LTE Router PN 001-0000-602 Rev. B