Ethernet Communication Loss

Dear All,
hope u all will be fine,
i have been facing a problem of ethernet communication loss on controllogix.
there is ethernet card 1756-ENB on controllogix. somtime it loss communication and on controller, I/O status begin to blink. if we unplug and again insert the card into the chasis, then it begin to start communication again.
we have replaced controller,ethernet card and chasis as well. but no vain, problem still there.
i will be thankful if any body help me.
thanks in advance.

I had a similar problem with siemens step 7. The machine would run and in the middle of a cycle or just sitting idle communication would be lost. After checking for lose connections on the bus and making sure everything was secure the machine still dropped out. On the advice of the oem we replace the main controller card and reloaded the program and the problem went away. I don't know if replacing the card fixed the problem or reloading the program. This problem reacuured about 6 monthes later and we did the same thing to fix it.

Also typically with communication problems its the device being pointed to the one before or after or the cables in between.

Make sure all your firmware is up to date, and turn ON auto-negotiate on all your devices.

Please describe your system a little more.

Processor
Processor Revision
Ethernet Module
Ethernet Module Revision

Is there ethernet comms to IO?

Is the ethernet module in the IO Tree?

Firmware first

Making sure you have up to date firmware is always a good idea. Some early versions of the ControlNet bridge card's firmware had a similar problem.

Can you describe the network setup? What types of devices are talking on the same subnet? Are you using managed switched or unmanaged gear?

From what you told us, I have two "shot in the dark" guesses.

Either an old ENBT module with a defective ASIC chip, OR and overburdened ENBT module with too much traffic for it's processor and needs latest EN2T module.

There are certain individuals who would argue that it cannot be a bad ASIC chip because Rockwell posted a technote on that problem years ago and EVERYONE has read and complied by now.

I could also be leading down the wrong path, but with the limited info, that is what I would check first.