Having problems communicating with 1761-NET-INI

[hdbob1340 0]

I am in the process of setting up a small network of mostly CompactLogix processors and a couple of SLC’s and a couple of MicroLogix 1000’s. I will be doing a small amount of messaging between processors and eventually have a SCADA system. I want everything to go over Ethernet. I am having a heck of a time getting the 1761-NET-ENI’s working properly. I was able to use the configuration utility and assign IP addresses using my serial cable. Once this was done there were no more fault lights and everything seems ok. I can find the 1761-NET-ENI using the Ether/IP driver but if I click on it, it goes unresponsive. If I use the Ethernet driver, it shows up with the dreaded red X. I’ve tried going online with a SLC 5/03 using who’s active and the Ether/IP driver and again things go unresponsive when I click on the device. Lastly, I am using an older version of RSLinx Lite, 2.43.01.23 (CPR 6) and my laptop is running Vista. I haven’t had any problems with any other drivers or versions of RSLogix except help menus while running Vista. Anyone have any ideas? Thanks!

[paulengr 44]

You won't be able to communicate using RS-Logix to the Micrologix PLC's through the NET-ENI using the Ethernet/IP driver. RSWho will work but that's it. Stick with the Ethernet ones. Start with the obvious though. Use PING to check your network connections, IP addresses, etc. If nothing else, take the NET-ENI completely out and set it up with either a crossover cable or a small Ethernet switch with NOTHING ELSE connected to it but your laptop on your desk. That way you can isolate and make sure of whether the problem is with the device configuration, cabling, etc., first before dealing with the rest of the network.

[mercedes98 0]

On RSLinx Lite: configure drivers, under available driver types select ethernet devices. On that driver, you're going to add every Host Name address (ex. 196.196.196.230) When you're finished with that you will save that by clicking Ok. After that, go to properties under Local Area Connection and select Internet Protocol (TCP/IP) and click on Properties. Change "Obtain an IP address automatically" to "Use the following IP address" and under IP Address (ex. 196.196.196.240), under Subnet Mask (ex. 255.255.0.0) and then click OK. Go Back to the RSLinx Lite and under Ethernet driver you should see all PLC connections. I hope this helps a little bit!

[hdbob1340 0]

Mercedes98, That helps alot actually. Could you explain readdressing from automatic to entering a manual address a little more in depth? Does the address need to relate to the configured address of the NET-ENI in some way?

[paulengr 44]

"Automatic" addresses are virtually NEVER what you want for industrial Ethernet. The way that this works is using BOOTP or DHCP. Any device configured this way when it first boots up/connects will send out a broadcast packet requesting an IP address. A local DHCP/BOOTP server on hearing the broadcast packet then sends a response with an IP address, gateway, and mask in it. This automatically sets up the device. However, the normal function of a DHCP/BOOTP server is to send out "dynamic" addresses. In other other words, random addresses from a pool of available ones. Every time the device powers or becomes disconnected and comes back, it MAY end up with a different IP address. Most modern DHCP/BOOTP servers will make an attempt to assign the same IP addresses but there's no gaurantee. The issue here is that when you go to set up RS-Linx, MSG commands, other PLC's, etc., what IP address do you use? You can't know. It's "automatic", and random. This is fine for office PC's and maybe HMI's but it is a total disaster for a controls network because you can't know what the correct destination addresses are. Hence the reason for the "normal" configuration (manual). Manually put in an assigned IP address, mask, gateway, etc. There ARE ways of getting around this problem with DHCP. And no, simply doing assignment by MAC address which is what 99.999% of the DHCP servers out there support is NOT the best way. It leaves you with no ability to swap hardware unless you control the DHCP server (and train your electricians on how to reconfigure it), and it leaves you with a single point of failure issue where your controls hardware is now relying most likely on a highly unreliable Windows server. One blue screen of death and your entire controls network comes to a screeching halt over the course of a few hours.

[hdbob1340 0]

Thanks to all for the help! Everything is up and working now. Just a few comments from my experience that may help others that are new to the 1761-NET-ENI and Ethernet networking with PLC's: 1) You must use a crossover cable when connecting directly to an Ethernet device from your PC (Ethernet switches excluded) 2) You don't need the latest version of RSLinx to communicate with these devices, nor is Windows Vista an issue 3) Use the regular Ethernet driver in RSLinx; it allows you to see all of your devices, not just the NET-ENI 4) Don't use any dynamic addressing and change the IP address on your computer to a manually set address that is consistent with the addressing protocol of the rest of the system 5) I had to make up my own Ethernet cables for this project and it took a bit of practice. I was also set straight on the wire assignments by a good IT guy