IP conflict / Cosy 131


We will be installing a new Cosy 131 at our site soon and have been informed by the vendor that there will be an IP conflict with the addresses provided.

With existing ewons onsite we have only assigned one IP on our range for the WAN to allow VPN access but the PLC / HMI will have data available via a web page that need to be viewed internally. The original plan was to assign the PLC / HMI & WAN IPs in the same vlan,

From posts on this forum it looks like that will cause an issue, so the proposed solution is to have have two connection from our network to the ewon.

  1. One from our switch to the WAN to allow VPN access on one vlan used for plant devices for example

  2. Another from our switch to one of the LAN ports of the ewon on another vlan to allow us access to the PLC/HMI.

If the PLC / HMI have addresses for example on and are connected to ports 1/2 on the ewon. Port 3 is connected to a port on our switch configured for vlan .105 range. And port 4 (WAN) is configured for and connected to a port on our switch configured for vlan .8 range

Will this work
Is there likely to be a conflict with the above proposal ?
Is there an issue having multiple connections to the ewon from our switch?
Are there any configurations that need to be done on the ewon to allow the above proposal?


If your WAN is 10.151.8.x/24 and your LAN is 10.151.105.x/24 you wont have a conflict. All LAN devices will must be in the same subnet to be accessed.

Hi Zach

If the ewon WAN is 10.151.105.X

And the
ewon LAN is 10.151.8.X
HMI 10.151.8.X
PLC 10.151.8.X

This would allow for two connections to the ewon from our switch one for the WAN to a port configured for subnet .105 for and another to a port on subnet .8.

Is this correct?

Will there be any issues with this?


Those address are fine. If they are all going through the same unmanaged switch you will have a problem those.