Unknown IP showing up in RSLinx

I have a setup with a number of Micrologix PLCs on the company network, using the Ethernet Devices driver in Linx for programming. Everything works fine normally but sometimes all of a sudden I can no longer download to one of the PLCs. When I look in System Comms or RSLinx I see that some weird IP address has been added to the bottom of the Ethernet Devices driver with a station address of 254.



I can easily delete the unknown IP and switch back to the correct one, but I have no idea what this IP points to (I know it isn't a PLC) and a ping produces no response. Does anyone know what could force an IP to be added to the driver in RSLinx?

What is the weird address?

When you configure your drivers try selecting "Ethernet/IP Driver" instead of "Ethernet Devices" as your driver type. The Etnernet/IP driver will find the PLCs for you and they'll show up in RSWho, you don't have to add the IP address to a list. You can actually configure and run both drivers at the same time if you like and then tunnel down the tree in RSWho.

My picture doesn't show the right addresses--the IPs we have set up in the driver are 10.21.33.xxx where xxx ranges from 201 to 210. The "weird" IP that shows up at node 254 is always 10.21.77.77. The subnet mask of our PCs is 255.255.0.0, which I cannot change.

I've tried using the Ethernet/IP driver in the past but have had some problems with it... "diagnostic status failed" errors as I recall. The Ethernet Devices driver seems to be more reliable except for this IP problem.

I never saw this, but try to delete driver, shut down linx, delete harmony files, reboot, add driver again.

Okay Kolyur. I don't know where the x.x.77.77 is coming from, but it sounds like either registry corruption, or some odd corruption in Linx itself.

The direct "AB Ethernet" driver should never scan for devices, they all need to be manually added. I was actually wondering if you had a loopback or diagnostic address stuffed in there somehow.

Check out the regrestry, and see if there is anything odd there... Maybe delete the driver and the key from the registry, then re-enter it?

Key is:
HKEY_LOCAL_MACHINE\SOFTWARE\Rockwell Software\RSLinx\Drivers\AB_ETH\(Assigned Name)\Node Table

Also, make sure you don't have duplicate keys under the RSLinx Drivers hive in the registry.

Hrm... shouldn't happen, but it's possible that a DDE/OPC topic was pointed to that address at one time.

I've had this happen before.


If the device was once configured, and a rswho browse was executed, then the ip address deleted from the driver but not the tree, it would get added like this.

How did I fix it?

First turn off auto browse.
Then remove the device out of the rswho tree.
Then remove the device from the ethernet driver.

Now go and browse. It doesn't return nor get added to the ethernet driver.

Hope this works for you too.

Thanks guys, I'll try out your suggestions.
Good tip about the registry, I didn't realize the drivers could be modified from there.