Using the Ethernet Gateway 4 on a private MODBUS TCP or SNMP Network

If you are using your Ethernet Gateway 4 on a private MODBUS TCP or SNMP network (Default Interface disabled)

Using the Ethernet Gateway 4 on a private MODBUS TCP or SNMP network

The Ethernet Gateway 4 offers MODBUS TCP and SNMP Interfaces which you can poll to receive sensor data for retrieval in MODBUS TCP or SNMP networks. These interfaces are disabled by default, but they can be enabled through iMonnit software or through the local configuration page (HTTP Interface) of the gateway when a static IP address has been configured on the gateway. The Default Interface (iMonnit Online) is always enabled by default, but can be disabled if operating the gateway on a private network on which Monnit software is not being used (iMonnit Online, iMonnit Enterprise, iMonnit Express, or Monnit MINE). When enabling these interfaces for use when the gateway cannot communicate with Monnit software, there are special considerations. This article will provide insight into these considerations and steps for operating your gateway with this configuration.


Disabling the gateway’s Default Server Interface

Note: the gateway’s firmware should always be updated prior to disabling the gateway’s Default Interface to ensure the gateway’s most up to date interface operation.

In order for the gateway to continue to receive sensor data and respond to polling on the MODBUS TCP/SNMP Interface while the gateway is not sending data to Monnit software, the Default Interface must be disabled. You may find that you are not receiving sensor data or that your gateway stops responding to polling on the MODBUS TCP/SNMP Interface intermittently if there is no connection to Monnit software, but you have not disabled the Default Interface.

As mentioned in this article, you will need to Unlock your gateway in order to disable the Default Server Interface. If the gateway is not Unlocked, you will not see the option to disable this interface. If this interface is left active while operating on a private network on which the gateway is unable to reach a Monnit server, the gateway will continually reach out to iMonnit Online unsuccessfully, and the sensor network will go inactive. This will be demonstrated by sensor data not being updated in the device’s sensor registers, and the sensor LED (top LED) will go dark.

Once the gateway is Unlocked, you can disable the Default Server Interface by accessing the gateway’s local configuration page (HTTP Interface) through a browser, clicking the Data Interfaces tab, selecting Default Server Configuration, turning it off, and clicking Save Changes. When the gateway reboots, it will no longer attempt to report data to Monnit software.

Data Interfaces offered by the gateway

The Ethernet Gateway offers 5 data interfaces.

  • Default Server Interface (iMonnit Online, iMonnit Enterprise, iMonnit Express, and Monnit MINE).
  • MODBUS TCP
  • SNMP
  • SNTP (Simple Time Network Protocol)
  • HTTP Interface (local configuration page)

HTTP Interface
HTTP Interface

Default Server Interface
This is the Interface on which the gateway sends data to iMonnit software. With default configuration, the gateway’s Default Server Interface is enabled to communicate with the iMonnit Online portal over the Internet on TCP port 3000. The gateway can be Unlocked and Pointed to communicate using the Default Interface to a local Monnit software such as iMonnit Enterprise, Express, or MINE. It is important to consider that the gateway will (generally speaking) need to first communicate with the iMonnit Online portal in order to be Unlocked and Pointed. That is to say, in most cases the gateway will first need to be connected to a network which allows for an Internet Connection over TCP port 3000 in order to be configured to operate with a local version of iMonnit software. In any case, the Default Interface represents a connection to Monnit software.

MODBUS TCP
The MODBUS TCP Interface is a read-only interface on which the gateway can be polled to provide gateway and sensor data on an Ethernet MODBUS TCP network. Modbus TCP is a non-streaming data interface standard. This means data must be requested in order for it to be received. The MODBUS TCP Interface will store all data values in 16-bit registers. In order to poll the data, a static IP address must be enabled on the gateway. This interface can be activated through Monnit software or using the local configuration page (HTTP Interface). The MODBUS TCP Interface does not support Slave ID configuration.

SNMP
The Ethernet Gateway 4 includes a SNMP V1 Interface which offers the ability to poll the gateway for sensor data using the SNMP protocol. By default, the community string for the gateway is “public” which can be configured using the local configuration page (HTTP Interface). The gateway supports the Walk command, and the MIB for the SNMP Interface can be downloaded at the link below. There is also an Internet MIB to decode the SNMP data. In addition to the main SNMP Interface, the gateway also offers the ability to send SNMP Traps to a specific endpoint. This can be enabled through Monnit software or using the local configuration page as well.

https://monnit.azureedge.net/content/downloads/MONNIT-EGW4.mib

SNTP
!Important! Note: If you disable the Default Server Interface, you must configure the SNTP Interface in gateways with firmware prior to version 1.0.5.5. In earlier versions of the firmware, your gateway’s sensor network will be disabled unless the status “On and Synced” in the gateway’s local configuration Status page for SNTP. If the status shows only “On”, the gateway is not able to retrieve time from the SNTP server. The sensor network LED (top LED) will also not illuminate in this case. You will either need to update the gateway’s firmware through the iMonnit Online portal to version 1.0.5.5 or later (which does not require SNTP when the Default Server Interface is disabled), or enable SNTP on the gateway and point to a valid SNTP server on the network.

A SNTP (Simple Network Time Protocol) interface is included on the Ethernet Gateway 4. SNTP is a synchronized computer clock on a network. A SNTP server can be set up on the same LAN as the gateway, such as on a router or a computer (Windows includes a SNTP service). The gateway should be configured to retrieve time from only trusted servers, such as those maintained by your ISP. Incorrect time can affect the delivery of sensor traffic. If the Default Interface is active, it will be utilized for time synchronization in ordinary operation. Therefore, SNTP will be used as a backup.

HTTP Interface (local configuration page)
The gateway also offers an HTTP Interface which allows you to access the gateway’s local configuration page. Details on how to access this page can be found at the following link. Ethernet Gateway 4 - Accessing local configuration page (HTTP Interface) Locally

Configuring sensors

It is important to understand that the single interface which offers the capability of configuring sensors is the Default Server Interface. Since this is the only Interface by which sensor configuration can be delivered to sensors, some form of Monnit software is required to change sensor configurations from their default settings. The most commonly changed sensor configuration is the sensor’s Heartbeat and Aware State Heartbeat. By default these are set to 120 minutes. Therefore if you are looking to operate your sensors with a more frequent heartbeat than 120 minutes (or any other configuration changes) while your gateway is operating on a private network with no connection to Monnit Software (Default Server Interface disabled), the sensor will need to be configured using Monnit software prior to disabling the Default Interface.

Note: There is no manner by which you can configure sensors using the gateway’s local configuration page (HTTP Interface).

This means that if you wish to modify sensor configurations in the future, the Default Interface must be enabled and the sensor will need to be configured using some form of Monnit software. For customers that do not have the option of connecting the gateway to the Internet, you may consider running a local version of Monnit software such as Enterprise or developing software using the MINE SDK.

This also means that your sensor heartbeat configuration will be limited by the version of Monnit software you are using to configure the sensors. Currently, the minimum heartbeat for a sensor using iMonnit Online 1 minute (if you purchase and apply iMonnit HX Credits ) or 10 minutes with a standard Premiere license. The local versions of Monnit software (Enterprise, Express, MINE) allow for 1 second minimum heartbeats for most sensors.

Conclusion

The interaction between the Default Server Interface, MODBUS TCP/SNMP interfaces, Unlock status, SNTP, and sensor configurations are critical to a successful implementation of a gateway on a private MODBUS TCP or SNMP network. This article should be useful in understanding these details, but if you have further inquiries feel free to contact Monnit Support.



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