Allen-Bradley 1734-AENTR Ethernet Redundancy

[hardaysknight]

We have a lot of POINT-IO modules in various places all over our machines. Occasionally one of the daisy chained cables between our 1734-AENTR will fail, bringing everything else on that network down.



What I'm wondering is if there is any way to have a redundancy using the 2 ethernet ports on the 1734-AENTR modules.


Currently they are all daisy-chained together. The current plan is to replace that and run all new dedicated ethernet cables to each 1734-AENTR back to the switch. I'm wanting to also leave the daisy chain in case one of the dedicated cables fail, it can fall back to the daisy chain.


Testing it with my test equipment, I've got a compactlogix going back to a network switch, then I have one 1734-AENTR running to the switch, and daisy chained to the second 1734-AENTR, however once I run another cable from the second 1734-AENTR to the switch, it brings the whole network down.

I'm thinking I may need a managed switch to somehow have a built in fallover, but IT here is useless so I really hope not.
I really hope that makes sense.

 

[Robobob]

Do a search for DLR ring information. If you have the correct hardware you can set up a DLR Ring that will achieve what you are asking. The AENTR,s and the correct CompactLogix will be all you need.

 

[the_msp]

You might need an ETAP (think that's what they're called).

Also, if you can, source your own switches like Stratix, that you have full control over. Dedicate a port as an uplink to the plant/corporate IT switch.

IT messing with switches that are for control-only purposes never ends well.

 

[Ken Roach]

The "R" in the 1734-AENTR part number indicates that its two-port hardware supports "Device Level Ring" fault-tolerant media. It's useful to think of DLR as a very fast, Rockwell/Cisco specific version of what good old Spanning Tree protocol did 20 years ago.

https://literature.rockwellautomation.com/idc/groups/literature/documents/at/enet-at007_-en-p.pdf

You'll need either a switch that supports DLR, or a 1784-ETAP module to connect up to a conventional switch, or to a CompactLogix that doesn't have a 2-port DLR feature.

When DLR is properly configured it's really good: you need to have two failed physical links to take down the network.

 

[JeremyM]

DLR is your answer, but be hesitant to try it on switched networks not set up for DLR/STP/RSTP; building a physical loop without the requisite layer 2 support will also bring down the network by broadcast storm.