What's the Procedure For Connecting to a PLC "Behind" Another PLC?

I'm talking about ... I'm on one network connected to the "primary" PLC, and this PLC talks to the one I need to get to, but I don't have direct access to that PLC "behind" it because it's on another network ... so I have to connect to it through the backplane somehow. The PLC I need to get to is listed under the I/O Configuration "tree" in the left pane. You'd think you could just right-click on it and choose "Connect", but you have to use RSLinx somehow, IIRC.

Could use a USB to Ethernet adapter and have a second Ethernet port on your PC?

http://www.plctalk.net/qanda/showthread.php?t=87369

Are the on a two physical different networks or do they just have different IP address?

geniusintraining said:

Could use a USB to Ethernet adapter and have a second Ethernet port on your PC?

http://www.plctalk.net/qanda/showthread.php?t=87369

Are the on a two physical different networks or do they just have different IP address?

Click to expand...

Maybe that would work, too, but I just found it:

You have to go into RSLinx, find the address of the PLC you can connect directly to, then drill down below "Backplane" to "Ethernet", right-click on "Ethernet", select "Properties", then ADD the IP Address of the PLC "behind" it that you're trying to (indirectly) access.

Then - once this address appears below "Ethernet", you open the application of the PLC you're trying to connect to, but then you click the Network Button at the top (beside the Path box) and drill down through the PLC you can directly connect to (NOT the indirect PLC) ... until you find the address you just added to that PLC. You have to drill WAY down ... Backplane, Ethernet, then Backplane again until you reach the indirect PLC ... then the "Go Online" button gets activated and it'll connect!

Hurray!

Should be easier than that, though ...

Glad you got it, thats one of the reasons I was asking if it was a different network physically or just addressed

geniusintraining said:

Glad you got it, thats one of the reasons I was asking if it was a different network physically or just addressed

Click to expand...

Oops! I missed that part in your post. For some reason, my eyes stopped at the underlined thread link! LOL!

But you raise a good question. I was plugged into a standard "Office Net", then RDP'd to a laptop that was directly connected to the "first" PLC's IP network.

The 2nd PLC had a different 2nd octet number in its IP address, but the 1st PLC was able to communicate with it. So by adding the IP of the 2nd PLC to the 1st PLC's "Ethernet" node, I guess I was defining the network path to it for RSLinx?

Why isn't RSLinx smart enough to do that itself, though? If two PLCs can communicate with each other, why can't I open the application of the "hidden" PLC, and just wait for RSLinx to find it? Shouldn't it be smart enough to figure that out?

Colt Hero said:

Oops! I missed that part in your post. For some reason, my eyes stopped at the underlined thread link! LOL!

Click to expand...

Welcome to the reading to fast club... I am also the president of typing faster than you can think club

Colt Hero said:

The 2nd PLC had a different 2nd octet number in its IP address, but the 1st PLC was able to communicate with it. So by adding the IP of the 2nd PLC to the 1st PLC's "Ethernet" node, I guess I was defining the network path to it for RSLinx?

Why isn't RSLinx smart enough to do that itself, though? If two PLCs can communicate with each other, why can't I open the application of the "hidden" PLC, and just wait for RSLinx to find it? Shouldn't it be smart enough to figure that out?

Click to expand...

First thing I do when looking at a network issue is try and figure out if there is a path, if yes then its just a addressing issue. As far as RSLinx, I think it can do so many things that its hard to do everything on its own... I use to run OEM version because it did a lot of different things that I needed (now using Lite) I THINK they are the same just the key uplocks features but I agree, I think they could make a dumbed down version for just standard communication, its really good software once you get to know it.