Frequently Asked Questions

GPRS Modem switching default gateway
Last Updated 3 years ago

If you have a JACE set up on site and are using port forwarding or NAT on a router to access it remotely via the internet, then you must also consider the following if you also intend to fit the GPRS Option card for sending SMS messages.

Basic IP networking fundamentals dictate that a single device can only have a single default gateway. (For an explanation on how this works, a quick google of ‘the default route’ should help you out.) However recently we experienced a case where a SIM card came live in the GPRS modem card, but the settings were such that it changed the JACE’s default gateway to its own, thus killing our existing remote connectivity over the internet via port forwarding from an on site router to the JACE’s LAN1 port.

The simple fix here is on the property sheet of the GPRS Modem card and is a tick box that says “Switch default gateway” or similar. This must be UNTICKED if you are remotely accessing the JACE via its own LAN ports over the internet.

In fact, if you are only using the GPRS card for SMS messaging then I suggest that you disable the PPP connection altogether since it will allow the modem to try and obtain a stable GSM only connection rather than ‘hunt’ for a potentially weak GPRS signal and periodically dropping out.

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