Author Topic: Auto Negotiate IP  (Read 889 times)

Lorne Van Dusen

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Auto Negotiate IP
« on: February 26, 2018, 06:56:00 PM »
This is just a general question in regards to PLC scan time as I figured it would be a question that might necessarily get asked by someone.
If you set the IP address to 0.0.0.0 to allow a router to assign a IP address to the PLC and a router is not connected or for some reason is powered off does it affect the scan time of the PLC as I would assume that the PLC is constantly queering the router for a IP address?

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Re:Auto Negotiate IP
« Reply #1 on: February 26, 2018, 07:14:58 PM »
Note that the 0.0.0.0 IP address setting is only available to SmartTILE-Fx based PLCs (Fx1616-BA, Fx2424 and EZWire1616).

SmartTILE-Fx CPU board will only query for the IP address when it is first powered up. If the router is switched OFF then the PLC will not be able obtain a DHCP assigned IP address and therefore will become offline. It does not periodically request for IP address from the router so there should be no effect on the scan time after the PLC has been powered up.

Since in many applications the PLC is not connected to the router when in operation this design concept is to prevent the PLC wasting precious CPU cycle to query for IP address from router that it is not connected to.

For applications that are connected to a router we do recommend selecting a fixed IP address that it outside of DHCP range to ensure that the PLC is reachable regardless of when the router is powered up. Otherwise you will need an LCD display to inform user of the IP address that it obtains from the DHCP server before you can connect to it.
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