Technical Notes

» » » Airgate-3g Operating As A Router For A Fieldlogger



1.1 Objective:

To use the AirGate-3G router to access HTTP service (pages in dynamics HTTP) hosted on the NOVUS FieldLogger equipment.


In this scenario, the FieldLogger is connected by cable to a router with 3G connectivity (the AirGate-3G). It is necessary to configure the port forwarding in the NAT table of the router so that it can properly forward the requests from the FieldLogger.

The router's IP address for the WAN interface is assigned by the telephone network carrier, therefore, because this IP address is dynamic, after every change to the IP address it would be necessary to reconfigure the supervisory software. To avoid this problem the 3G router should use a Dynamic DNS (DDNS) server that translates a dynamic IP into a URL address (HOST). Therefore the FieldLogger needs to maintain the same IP address (static or behind the DHCP server configuration) for the configuration to work correctly.


Figure 1 - Network Topology



Some of these services are subscriptions and others offer limited plans for free. Basically these services attribute a friendly name to the IP address used by the router. To configure the DDNS server [see tutorial TCN001-15]. It is still necessary to define/configure the following parameters:


  • IP of the AirGate-3G: In the case that there is a DDNS service, it is possible to use this directly to host the service. In this tutorial we use the dynamic IP assigned by the telephone carrier.


  • IP of the FieldLogger: The IP of the FieldLogger should always be the same. This can be either assigned through the DHCP server or can be configured statically on the FieldLogger.


  • Service port on the FieldLogger: The default service port for HTTP is port 80.


1.2 Verify the status of the AirGate-3G:


Verify the status of the connection through the system tab, in the web GUI configuration for the AirGate-3G. If the RUN LED is GREEN/BLINK this indicates that the router is ready, as indicated in Figure 2. For more information on how to access the configuration interface of the AirGate-3G, download the manual: 


Figure 2 – Indicator LEDs.


Under the tab Current WAN Link, it is possible to verify the IP address assigned by the telephone carrier, as can be seen in Figure 3.


Figure 3 - Current WAN Link.


As can be seen in Figure 4, under the tab Cellular Information, it is possible to verify the general status of the modem, including the APN, carrier and signal quality.


Figure 4 – Cellular Information


1.3 Configuration of the AirGate-3G:


In this tutorial, we will use the DHCP server of the AirGate-3G to assign an IP address to the FieldLogger. Under the Eth1 tab it is possible to verify the IP configuration for the AirGate-3G router in the IP address field (see Figure 5 ); and under the DHCP Server tab, the range of IP addresses assigned to the DHCP. Note that the IP address assigned to the FieldLogger is displayed in the IP lease section, as shown in Figure 6. The value shown in the MAC address field should correspond with the MAC address of the FieldLogger.


Figure 5 – LAN Interface Eth1


Figure 6 – DHCP Server and address leases.


It is necessary to configure the NAT table in the port forwarding to send connection requests to the desired service ports. In Figure 7, all of the connections are being routed to the service port 502 [for communication/configuration] and port 80 [HTTP services].


Figure 7 – NAT Configuration.


  • Arrives at Port: Entrance port for the AirGate-3G [Created by the Administrator], for service access to the equipment; (Check ports already used by other services)


  • Is Forwarded to IP Address: Directs the request from the arrives port to the IP address of the equipment in use [FieldLogger];


  • Is Forwarded to Port: Service port of the equipment [FieldLogger].


1. Configuration of the FieldLogger:


After verifying the configurations of the AirGate-3G  and checking the electrical connections, we need to configure the network interfaces of the FieldLogger as shown in Figure 8. For more information please download and consult the operations manual:



Figure 8 – IP Configuration.


In the configuration of the FieldLogger equipment, in the Ethernet Interface it necessary to enable HTTP services [To enable the presentation of dynamic HTML pages] and Modbus TCP [for communication and configuration of the equipment and to allow access to SCADA software]. This can be seen in Figure 9.


Figure 9 – Configuration of HTTP and Modbus TCP


1.5 Summary:


Using this tutorial, it is possible to remotely Configure FieldLogger equipment, Monitor variables through HTTP service, Collect data from the device memory and Display the information through SCADA software. Figure 10 demonstrates different ways to connect to the internet: Wired connection, connection via a WIFI router or access through the cellular network using a mobile device with a 3G data plan.


Figure 10 – Connections and Access to the Internet.

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