Local PLC Connection Problems

JCreel

Member
Join Date
Apr 2020
Location
Mississippi
Posts
51
Hi Everyone, so i got a bit of a head scratcher, i cant connect to any of my PLCs on a local network....

For instance, i have a work bench in my office to do all of my PLC testing and training, and i have multiple remote racks, and different IO modules all connected over ethernet. I always just connect locally to my test bench when im trying something new. However, as of this morning my comms just stopped working.

Here's whats weird, my IP has not changed, ive tried multiple drivers on my computer, ive bypassed the ethernet switch and went straight to the device, and i have re-installed rockwell software,

But it gets weirder, i can ping all of the devices on my network via command prompt and get a response from them all. However, i cant put the IP in a web browser and pull it up?????

I also tried using RS linx and Factorytalk Linx, and both will show the devices in the tree.......But you CANT drill down the backplane. I also took a spare computer with no software on it, and connected to my network and searched all my devices in a browser and all of them pulled up.

Im also connected to our plants PLC network as well, and i can go online and view all of those problems without a hitch, which makes me beleive its not software related.

Not sure if this is windows related, but has anyone seen this, or know what could cause this?
 
sorry for your loss.
But, it makes me happy that I don't use AB anymore.
Not trying to be mean.
Can you connect via the programming software?
Or is it a java issue?
 
I'd disconnect all devices except one and connect to it. If successful, add one at a time.

Seems like one device is throwing RSLinx, or windows, a problem. Some kind of a loop, perhaps a switch and router connected with 2 cables. Maybe a duplicate IP. I'm grasping at straws, obviously.
 
sorry for your loss.
But, it makes me happy that I don't use AB anymore.
Not trying to be mean.
Can you connect via the programming software?
Or is it a java issue?

I believe its something computer related. The programming software will not connect over the local network either.
 
I'd disconnect all devices except one and connect to it. If successful, add one at a time.

Seems like one device is throwing RSLinx, or windows, a problem. Some kind of a loop, perhaps a switch and router connected with 2 cables. Maybe a duplicate IP. I'm grasping at straws, obviously.

I disconnected all devices and took my PC off the dock and hardwired directly to my EN2T card, and its still doing the same thing. I can ping it and see it, but cant do anything with it. See pictures

2022-01-07 12_19_34-Window.png 2022-01-07 12_19_58-Window.png 2022-01-07 12_20_57-Window.png
 
The problem is limited to your engineering PC and your test bench setup, correct ?

Are you using a built-in Ethernet port, or a USB "dongle" type adapter ?

I strongly prefer an "IP Scanner" tool like Angry IP Scanner or Advanced IP Scanner instead of the ordinary command-line ICMP Ping tool. Set them up to do both ICMP Ping and to check TCP Ports 80 (HTTP), 502 (Modbus), 2222 (A-B legacy Ethernet) and 44818 (EtherNet/IP).

Do you use any VPN software ? Maybe something that got updated recently ? Certainly those can interfere with various types of network traffic.

Your system sounds like maybe IPv4 has gotten unbound from the local adapter, or is being rerouted through a VPN connection.
 
Instead of ping, try

telnet 192.168.1.250 44818


(you may need to install telnet). Also, instead of 44818, try 80 and 502.


What is the error message?
 
Whenever I find a plc software cannot connect to a device over ethernet but still finds it.....and you can still ping it (few times in my career) it has almost always been duplicate ip adresses. Either you have some dhcp server somewhere that assigned an ip to some devices fixed ip that was existing......or some "IT PROFESSIONAL" put a CAT cable Loop into an ethernet switch somewhere.
 
So after some research i found that my firewall was blocking rockwell traffic from my local drivers. Not sure how this happened, but i had to go and manually add the apps back into my firewall setup.

I didn't find this until after i redownloaded software, scanned the IP net, and restarted my PC about 8 times. After i did that and rebooted everything came back like normal. Very odd, I've had this PC about 2 years and have never seen this particular issue regarding Rockwell software.

I appreciate all your time on helping me get this fixed
 
In the future, it might also work for you to install wireshark on your PC, when issues like this happen, you can use this capture filter: "host xxx.xxx.xxx.xxx" where x fills the IP address.

When trying to use the software, if red error messages pop up, that means that it's likely a port thing.
 
Check Firewall setting, may be blocking connection, also check IP is not duplicate you could check that you are seeing right MAC with ARP -a

Strip it back to a HUB + CPU + cables and see if it warks
 

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