EIP21 Network Issues

[NathanC 0]

Hi All, I have a number of CJ PLCs on an EIP network. I have an issue with two of the PLCs flooding the network trying to send data to an IP address 239.192.7.0. The IP range of all the PLCs are different to this and I cannot find any setting within the EIP cards with this IP in it. I have spoken to Omron and they suggest replacing both CPUs. Just wondering if anyone else has encountered this issue before. Thanks,

[Ken Roach 194]

You do not need to replace the CPUs. This is a very common configuration issue. What you are seeing is a multicast IP address, and it's used by EtherNet/IP Produced data connections when they are going to be consumed by multiple consumers. Constraining multicast traffic using IGMP Snooping and IGMP Queriers in managed Ethernet switches is a basic principle of EtherNet/IP I/O systems. There should be copious amounts of Omron documentation on the topic. The easiest way to constrain multicast traffic is to not use it if you don't need it. I don't use Omron controllers, but with A-B controllers they eventually made "use unicast" the default connection method, and you have to specifically configure an I/O module connection or a Produced/Consumed Tag to use Multicast if you want to have multiple simultaneous consumers or Listen-Only connections. Edited 11 Mar 2014 by Ken Roach

[Ken Roach 194]

A nice tutorial I found just Googling: http://www.myomron.com/index.php?action=kb&article=1416 You'll see the "Multi-Cast" versus "Point-to-point" selection about 2/3 of the way down. If the Ethernet DataLink configuration software described in that tutorial looks familiar, you should be able to find the connection and change it, or at least understand what's going on with your network better.

[NathanC 0]

Thanks for your help Ken.

[lostcontrol 23]

What is the specific issue you are having? Are you having bandwidth issues, or these 2 PLC's behaving oddly?

[NathanC 0]

The issue was actually with a trio radio I introduced to the network locking up. after spending some time trying to work out what was wrong with the radio I ran wireshark and noticed the two PLCs continuously sending to the above IP address. I have since changed my EIP setup to be point to point instead of multicast. The trio radio is now working.

[Ken Roach 194]

Thanks for the followup ! Radio networking is definitely one of the things you need to be careful with when there is multicast traffic. Glad to hear you got it sorted out.